NOTES AND MEMOBANDA. 289 



Neapolitana the extrusion of two germinal vesicles precedes the seg- 

 mentation of the yolk ; this gives rise to four pear-shaped parts of 

 equal size, which divide towards their narrower end into four ecto- 

 dermal and four endodermal cells ; the latter are at first the larger, 

 but the ectodermal cells increase rapidly in size and form a cap over 

 the others. The endodermal cells, as they multiply, become arz'anged 

 in two rows, and gradually separate so as to form a cavity. The 

 embryo is convex on its dorsal surface, and there is a median groove 

 on the ventral ; the whole larva is covered by cilia, of which there is 

 a large tuft just in front of the eyes, and a smaller one at the hinder 

 end. The animal at this stage has consequently very much the 

 appearance of a Pilidium. 



Goette, from the fact that there are certain Nemertines which cast 

 their larval integument, like Pilidium, without having the form of this 

 larva, and that there are Dendroccela which pass through a Pilidium 

 stage without undergoing any true metamorphosis, concludes that there 

 are various modifications of this relatively simple process of develop- 

 ment, and that the developmental history of the Nemertines may be 

 referred to that of the Dendroccela. 



Organization and Development of the Oxynrids. — Dr. Osman 

 Galeb made a communication last year to the French Association for 

 the Advancement of Science on the Oxyurids found as parasites 

 in insects, which is now published in Professor Lacaze-Duthiers' 

 'Archives.'* Dr. Galeb has found difierent species of parasites 

 in different species of insects, notwithstanding the similarity of 

 habit in the hosts, and he draws more particular attention to the 

 mode of development, and to the genetic affinities of these parasitic 

 forms. 



The ova are easily studied owing to their great transparency ; the 

 germinal vesicle was not found to disappear at the period of segmenta- 

 tion, but to elongate and divide ; and indeed it is not till after its 

 segmentation that the egg begins to undergo the same process. The 

 enteric tube is formed by two swellings, which gradually meet one 

 another ; the more anterior forms the oesophagus and the commence- 

 ment of the intestine. The observations of the author on the develop- 

 ment of the generative organs do not agree with those of Schneider ; 

 his later observations lead to the conclusion that these parts are formed 

 by the proliferation of a cell in the abdominal region, and not by the 

 division of the primitive cells into a central (ovarian) and a peripheral 

 (investing and supporting) series. 



M. Galeb believes that as the various species of Orthoptera and 

 Coleoptera which he has studied have become differentiated from a 

 parent form, the parasite of that parent form has likewise become 

 differentiated into different species adaj)ted to their varying hosts. 

 With regard to these observations it may be interesting to draw 

 attention to the fact that Mr. A. H. Garrod, the Prosector of the 

 Zoological Society, has found a species of Tcenia in the Rhinoceros 

 from the Sonderbunds, which he regards as identical with the species 

 of this parasite found by Professor Peters of Berlin and Mr. Garrod's 

 * ' Arch. Zool. Exp. and Gen.,' v. (1878). 



VOL. II. U 



