zooLoar and botany, microscopy, etc. 425 



notes on the coelomic epithelium of Petromyzon fluviatilis ; in trans- 

 verse section the cells appear of a low cylindrical or of a cubical 

 form. From the descriptions of Langerhans it would seem that 

 P. planeri has retained the primitive form of coelomic epithelium 

 more completely than P. fluviatilis ; while the latter has a short cylin- 

 drical or cubical epithelium still present in the neighbourhood of the 

 parietal peritoneum, in the Amphibia the cells even of this region 

 have become flattened. The epithelium of P. fluviatilis varies some- 

 what with the season of the year. 



Fate of the Blastopore of Rana temporaria.* — Mr. W. B. Spencer 

 concludes from his observations 



1. That the medullary folds grow over and inclose the neural 

 canal, hut not the blastopore which remains open to the exterior ; 



2. That the hinder part of the neural canal which opens into 

 the blastopore loses its cavity, and the nervous system in this region 

 becomes solid ; 



3. That just in front of the blastopore the epi-, meso-, and 

 hypoblast are fused together ; 



4. That the blastopore never closes, but becomes transformed into 

 the adult anus. 



Primitive Streak in Osseous Fishes.f — From his recent observa- 

 tions M. L. F. Henneguy has been led to believe with Kupffer that 

 the embryos of Teleosteans possess a primitive streak, but whilst 

 Kupffer regards the longitudinal furrow as representing the streak, 

 Henneguy holds that only the caudal expansion (bourgeon caudal) be- 

 hind Kupffer's vesicle can properly be homologized with that primitive 

 organ. The primitive streak in Teleosteans is rudimentary, and 

 shows a striking analogy to that of reptiles, a class in which Kupffer, 

 disagreeing with Balfour and Stahl, has denied the occurrence of a 

 primitive streak at all. 



Formation of Egg-shell in Dogfish.^ — M. E. Perravex has investi- 

 gated the formation of the egg- shell in Scyllium canicula and S. 

 catulus ; the oviducal gland was supposed by Bruch to be concerned 

 with the production of the egg-shell, and subsequent investigators 

 have assigned its production to a particular layer in this gland. 

 Transverse sections through the egg-shell of a Scyllium show that it 

 is made up of a number of layers closely united ; the structure of 

 the median portion of the rndimental gland corresponds and is 

 doubtless the seat of origin of the egg-shell ; it is composed of a 

 series of layers between which open the glandular caeca whose func- 

 tion it is to secrete the formative matter of the shell. When the 

 ovum is set free from the ovary and falls into the oviduct it re- 

 ceives its albuminous coating in the superior portion of the rndi- 

 mental gland ; during this time the two walls of the median part 

 of the gland, being closely applied to each other, do not allow their 



* Zool. Anzeig., viii. (1885) pp. 97-8. 



t Ibid., pp. 103-8. 



X Comptes Rendus, xcix, (1884) pp. 1080-2. 



