large or small eggs, Chambers found from his study of sections of various organs and tissues (lens, ear-vesicle, rectum, epidermis, cartilage, muscle-fibers and blood-corpuscules), that the size of the cells of a tadpole or young frog is in direct relation to the size of the examined individual. This in general agrees with the results from my own work, which I hope to publish in the near future, on the cells of large and small salamanders. Since, as was shown above, the size of the embryo depends upon the size of the egg from which it develops, Chambers draws. the further conclusion that the size of cells of an animal is determined by the initial size of the egg from which it has developed. In another experiment, where eggs of R. temporaria were reared at two temperatures of 10° and 25° C., the tadpoles of the first set (10° C.) metamorphosed two months later than those of the second set (25° C.), but the young frogs developed in the medium with a low temperature (10°) were fully one and one half times as large as those developed at a higher temperature. Whether this large size was due to the low temperature or to the fact that the tadpoles had been growing two months longer before metamorphosing, this point is not made clear. However, on examining cells from the epidermis and rectum Chambers found that the differences in total size of frogs, developed at a high or a low temperature, extend also to their cells, so that large specimens have correspondingly larger cells than small specimens. But the initial size of the eggs and the temperature of the medium are not the only factors determining the size of the tadpoles and young frogs, because large and small individuals may develop even from eggs of uniform size and under similar conditions of temperature. What has been found in regard to the variations in size of the eggs may of course be also true in case of the sperms, which might thus be a factor determining the size of the young. At any rate, Chambers made an interesting observation that tadpoles developed from eggs of the same size begin to vary only after the supply of yolk has been exhausted and they have commenced to take in food. It is not improbable, therefore, that the variations in size result either from an insufficient amount of food available for some tadpoles, as is the case, for instance, in growing starfishes, or else the tadpoles may consume unequal amounts of food under different conditions of health. 3 3 Mead, A. D. On the Correlation between Growth and Food-supply in Starfish. It is a matter of some interest that Chambers maintains that the cells of large and small individuals developed from eggs of uniform diameter are not of different but of the same size. Thus he leads us to believe, and in fact he states it explicitly. at the close of his paper, that the principal factor determining the size of cells of an animal is the initial size of the egg from which it developed. In the Without giving mention to some objections to this general conclusion, which might be made on the basis of Chambers' own experiments, I wish to point out that the figures of cells given in the text do not carry conviction, and, so far as I was able to make out, they do not bear out Chambers' contention. drawings of cells of blood-corpuscles, epidermis and rectum, which Chambers thinks to be of equal size, I find on careful examination that the cells are different. Of course, actual measurements of the cells could make this matter clear, but, unfortunately, there are no measurements given in the paper. The introduction to the paper contains a résumé of a few works in one way or another related to the problem. This résumé of facts so widely scattered throughout the literature will doubt less be found useful. The third part of the paper is devoted chiefly to extensive theoretical considerations and does not therefore come within the scope of the present review. In conclusion I should like to call attention to some defects of a technical character, which obscure the meaning of the text and frequently confuse the reader. In the explana But tion to Fig. 1 it is said, for instance, that I marks a culture developed from eggs of similar size, and II marks those developed from eggs of different and not ascertained sizes. in the text referring to this Fig. 1 it is said that "Kulture II wurde mit Eiern angefangen, welche von gleicher, ausgesuchten Grösse waren.' the text or in the explanation to the figure, are the correct ones the reader is at loss to know, while the understanding of this point is important. On p. 635 we find reference to Fig. "A" and Aa in text Fig. 2. found to apply to Fig. a and aa in the Text-fig. 5. Which of these data, whether those found in As a matter of fact this reference was In Table Vin the third column the date of spawning is given as June 5, and the date of the first examination of the developing embryos is June 3. There is, however, a more vital contradiction in the text. On p. 620 in a discussion of the facts presented in Table I we read: "Die kleineren Eier zeigten eine geringe Neigung sich schneller zu entwickeln." On p. 647 referring again to the Table I we read: "In den Furchungs- und Gastrula-Stadien zeigen die kleinen Eier die Tendenz, sich wenigerschnell zu entwickeln, als die grösseren Eier." And further on, p. 647, and referring again to the Table I, we read: " Da wir nun aber gesehen haben, dass die grossen und kleinen Eier sich gleichgut und gleichrash entwickeln (s. Tabelle 1) etc." Thus it appears that the small eggs develop somewhat faster, and slower than the large eggs, and just as well as the large eggs! PARASITOLOGY SERGIUS MORGULIS. Cestodes of Birds. Fuhrmann has recently published (Zool. Jahrb., Suppl. 10, Heft 1) a most valuable monograph on the Cestodes of Birds. He had at his disposal all the material from the great European museums and from the private collections of prominent European helminthologists, so that the work is vastly more valuable than a mere literary revision with studies on limited personal collections. In 1782 Goze described 14 species of Tænia from birds; in 1819 Rudolphi listed 54 certain and 30 uncertain species, and in 1850 Diesing recorded 81 certain and 28 questionable species. Von Linstow's Compendium der Helminthologie and Nachtrag in 1889 gave references to 230 bird cestodes from 340 host species. In this investigation Fuhrmann had material from 200 more species of birds at his disposal and recorded in all some 500 cestode parasites from them. When one considers that 12,000 species of birds are known and Cestodes have been collected from 540 only, it is clear that many more new forms are to be expected; these are to come most prominently from extra-European lands. North America which Fuhrmann notes as relatively unexplored, will contribute its share and I may add that investigations in this field are already in finished manuscript as studies from my own laboratory. Some of the general conclusions which Fuhrmann has reached as a result of his 12 years of work in this field are of wide interest. The distribution of cestodes among the various group of birds shows that a given species occurs only in a given group of birds and hence is typical of it. Birds with similar food habits shelter often radically different cestode parasites both in species and in genera. On the other hand, related birds of different food habits often show similar genera among their cestode guests even though the species differ. A zoogeographic survey of the cestodes in the various groups of birds shows a sharp contrast between the species found in different regions and furnishes strong evidence of the value of parasites as aids in zoogeographic investigations. In this respect the cestodes are unquestionably of the greatest value in the light of Fuhrmann's studies. The It would be impossible to abstract the systematic portion of Fuhrmann's paper. Many of the doubtful and insufficiently described species of other authors are here positively evaluated after comparison of the original material. Each genus is characterized on the basis of the author's investigations and the type species designated. The other species are also listed with references to the appropriate literature and to all known hosts. faunistic section contains a complete list of the hosts with their cestode parasites and a record of the geographic distribution. A good alphabetic index of families, genera, species and synonyms, together with a full bibliography, closes the paper. Though not stated specifically, the monograph appears to be confined to the Cyclophyllidea and all will await with great interest the publication by this author of further studies dealing with other groups of avian cestodes. The In structure it A paper by Plehn (Zool. Anz., 33: 427) on a blood-inhabiting cestode designated Sanguinicola, is of especial interest both from the morphological and from the biological standpoint. animal occurs in the blood system of Cyprinid fishes, being most frequently found in the bulbus arteriosus, and was originally described in 1905 as an aberrant rhabdocol. agrees well with the few monozoic cestodes classed together as Cestodaria and often separated from other cestodes. The species does not reach full development in this host, or at least in the blood vessels, since no specimens with fully developed female organs have yet been found. withdrawn by some blood-sucking parasite and undergoes further development in that host. In view of the size of the worm and its evident inability to reach even the superficial arterioles, such a The author conjectures that it is perfect account of the structure of this worm makes any dis cussion of its precise genetic relationships unwise and the proposed phylogeny of parasitic flatworms based upon it has therefore only a purely suggestive value. The Harben lectures for 1908, which were delivered by Professor George H. F. Nuttall, of Cambridge, England, have been printed (Jour. Roy. Inst. Pub. Health, July-September, 1908). The topics covered are the ticks and the diseases which they transmit to man and domestic animals; the diseases are among the most important of those caused by animal parasites especially and are due to spirochetes, piroplasma and filaria. Nuttall's account, which is the most complete résumé available in this field, is notably lucid and scholarly in presentation. HENRY B. WARD. |