Miscellaneous. 523 



of the body), and in obtaining sections which plainly showed the 

 penetration of offshoots of the lateral nerves into the pharynx. His 

 most important point is the demonstration of the existence in the 

 connective layer of the pharynx of a large annular ganglion, which 

 exceeds the true cerebral ganglion in size, and this explains the 

 extraordinary mobility and vitality of the pharynx, which almost 

 seems to be an independent creature. 



The author further investigated the Cladocera and Copepoda of 

 the district, and also its Hydrachnidse ; among the latter he notices 

 his discovery of a new species of the genus tSperclion, Kramer, and 

 of a new Arrenunis. He also obtained two new Rotatoria and an 

 undescribed Turbellarian (belonging to the genus Prorhyjichiis). — 

 Zoologischer Anzeic/er, no. 206, p. 575. 



Note on the Blastodermic Vesicle of Mammals. 

 By Prof. A. C. Haddoi^, M.A., M.E.I.A. 

 The author suggests the view that in the blastodermic vesicle of 

 mammals at the close of segmentation the inner mass, since- it gives 

 rise to the embryo proper, is perfectly comparable with the germinal 

 disk of a fowl during the later stages of segmentation, which has 

 sunk into the blastodermic vesicle owing to the absence of yolk. 

 The outer layer corresponds to those epiblast-cells which are 

 gradually enclosing the yolk, the so-called blastopore of Van Beneden 

 indicating in an exaggerated manner the distinction between the 

 embryonic and non-embryonic germinal layers. Epiblast-cells 

 grow over this " blastopore " and form the covering cells (Decken- 

 zellen) ; eventually the invagination of the germinal area is recti- 

 fied, and there is a diploblastic ovum, the covering cells forming 

 the spurious third layer which misled Van Beneden. The segmen- 

 tation of the ovum is next discussed, and the conclusion is arrived 

 at that the first immigration of blastospheres into the interior of the 

 ovum (Van Beneden's stage 3) indicates the gastrula stage. It 

 would further appear that this immigration was asymmetrical, much 

 as there is an asymmetrical invagination of the hypoblast in telole- 

 cithal ova. The extension of cells of the blastodermic vesicle over 

 the embryonic area is probably to be accounted for, in most cases, by 

 the sinking of the latter into the cavity of the former. These 

 "Deckenzellen" are really a portion of the blastodermic vesicle, that is 

 of the yolk-sac, and they form the first adhesion between the ovum 

 and the parent. This is compared with the imperfect attachment 

 of the embryos of marsupials to the uterine wall, which is effected 

 solely by the yolk-sac, as has been recently demonstrated by H. F. 

 Osborn and by Caldwell. — Proc. Eoy. Dublin Soc. n. s. iv. pp. 636- 

 547. 



Note on Halcampa chrysanthellum, Peacli. 

 By Prof. A. C. Haddon, M.A., M.E.I.A. 

 In a paper read before the Royal Dublin Society on N^ovember 18, 

 1885, Professor A. C. Haddon withdrew the name applied by him 

 to a species of Halcampa from Malahide, co. Dublin (Proc. R. Dubl. 

 Soc. n. s. iv. p. 396, pi. xvi.). After having examined a number of 

 specimens it was found that this species is an extremely variable 

 one; its synonyms are : — H.{XantMojms') vittata. Kef.; H.{X.)hi- 

 lateralis, Kef. ; H. Kefersteini, Andr. ; //. Andresii, Hadd. A full 

 description and figure were given. 



