1006 SUMMARY OF CURRENT RESEARCHES RELATING TO 



ccelous. Its walls are exceedingly delicate, and there appears to be 

 no anus. There is appended to it what may be a salivary gland. 

 The animal fixes itself to the papilla of the venous system of the 

 Teiliys, and so obtains its nourishment. 



Prof, de Lacaze-Duthiers considers that Phoenicurus is a dendro- 

 coelous worm, but it is not yet possible to definitely fix its zoological 

 position, as he has not been able to study the history of its develop- 

 ment. He sought for generative organs in the month of May, but 

 was unable to discover them. It is possible that Phoenicurus is only 

 a period or stage in the whole life-history of the animal, and that its 

 development is accomplished under different conditions to any yet 

 observed. Next year the author hopes to be able to fill up the 

 present lacunae. 



RelationsMp of Rotifers and Nematodes.* — Dr. O. Zacharias 

 emphasizes the parallelism in the development of these two groups. 

 In comparing the segmentation of the ovum of Anguillula aceti with 

 that exhibited in the Philodinese, he noted the same unequal division 

 and epibolic gastrulation, and probably too, the same origin of the 

 mesoblast in the form of two small rounded cells near the blastopore. 

 The larva or the " palm-form " stage, with its expanded head portion 

 and narrowed trunk, is equally characteristic of both groups. The 

 affinity thus hinted at is corroborated by anatomical resemblances, 

 6. g. in the arrangement of the muscles and of the excretory canals. 

 The absence of cilia in the Nematodes is explained as a degenerative 

 change which finds its counterpart in the unciliated rotifer, Apsilus 

 lentiformis. 



In the embryos of Anguillula aceti Dr. Zacharias observed on 

 the trunk portion a superficial segmentation, which disappears as the 

 trunk or abdominal region proceeded to grow out at the expense of 

 the head. This process seems to him exactly comparable with the 

 development of, e.g. Pclygordius from the free-living TrochopJwra. The 

 expanded head-portion of the nematode and rotifer larva is, according 

 to Zacharias, the homologue of the head of the free-living Polygordius 

 larva ; on both rotifer-larva and TrocJiopJiora the cilia appear on that 

 head-portion. He opposes the possible suggestion that the head- 

 portion of the rotifer and Nematode larva is purely trophic, of physio- 

 logical and not of morphological import ; and maintains the common 

 origin of the two groups from an ancestral type resembling the " palm- 

 form " stage, with ciliated head-portion and long narrow tail or trunk. 



Development of Rotifers-t — Miss C. Pereyaslavtseff, the Director 

 of the Sebastopol Zoological Station, publishes an interesting paper 

 on this subject, which has been rather neglected, M. Zaleski's paper 

 on the history of the development of Brachionus urceolaris not being 

 a complete solution of the question. 



Miss Pereyaslavtseff's method differs from most of those hitherto 

 recorded ; she does not select one or another phase of development as 



* Biol. Centralbl., v. (1885) pp. 228-33. 



t Mem. Novorossian Soc. Naturalists, ix. (1884) 19 pp. (1 pi.). Cf. Nature, 

 xxxii. (1885) pp. 579-80. 



