ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 637 



Development of Gastropoda.* — F. Blocliinann first reports on 

 the development of Aplysia limacina, the ova of which are so trans- 

 parent as to need no special preparation ; their rate of development 

 is very slow. But, owing to his repeated references to his figures, 

 and to the account given by Eay Lankester, this portion of the essay 

 does not, without illustrations, admit of being condensed. The 

 author states that the most important result of his observations is the 

 demonstration of the agreement of A. limacina with the leading points 

 in the developmental stages of other Gastropods. 



Dealing, next, with the fate of the blastopore in Paludina vivipara 

 we find Blochmann disagreeing with Eabl, and agreeing with Lan- 

 kester and Biitschli in believing that the blastopore is directly con- 

 verted into the anus. Though among the Gastropoda the blastopore 

 and the mouth have generally a close relation, the doctrine here 

 supported finds analogous results in the history of the Annelids Serpula 

 and Salmacina dysteri. 



When we come to seek for an explanation of the varied fate of 

 the blastopore, we have to note that, in Aplysia, this orifice is elon- 

 gated, and that its hinder edge is, at a very early stage, brought into 

 close relation with the two anal cells, which mark the point of the 

 future anal orifice ; at the same time, the anterior end of the slit is close 

 to the oesophageal invagination ; in other words, it extends over the 

 whole of the ventral surface, just as is the case in Peripatus (Balfour). 

 The author thinks that BUtschli's idea, that the blastopore corre- 

 sponds morphologically to the oral and anal orifices of the Metazoa, is 

 necessary to the Gastrsea-theory ; it is, at least, to be noted that, not 

 only does the blastopore occasionally in all groups correspond to the 

 anus, but in one great division — that of the Echinodermata — it always 

 does so correspond. In the Entomostraca we have the Gladocera in 

 which the blastopore and mouth correspond in position, and the Cope- 

 poda in which the anus and blastopore so correspond ; insects have a 

 slit-shaped blastopore occupying the ventral surface, and even in the 

 lower Vertebrates we find, as Balfour and Hatschek have especially 

 shown, that the blastopore is, in many cases, an opening of an elon- 

 gated form. 



Liver of Gastropoda.f — The researches of D. Barfurth have led 

 him to the following conclusions : In Arion and Helix the liver is a 

 compound acinous gland, the parenchyma of which is sui-rounded by 

 a lacunar serous layer, a muscular layer, and a circular tunica pro- 

 pria. The unilaminate epithelial investment of the follicles consists 

 of ferment, hepatic, and calcareous cells. The liver is nourished by 

 the hepatic artery, the final branches of which terminate in the spaces 

 in the connective tissue, and these communicate with the blood-sinus 

 which surrounds the liver. The epithelial investment of the gall-ducts 

 consists of ciliated and mucous cells ; but at some points cylindrical 

 epithelial cells are alone developed. Special nervous structures are 

 to be observed in the liver, where they have the forms of large cells, 



* Zeitschr. f. Wiss. Zool., xxxviii. (1883) pp. 392-410 (1 pi.)- 

 t Arch. f. Mikr. Anat., xxii. (1883) pp. 473-524 (1 pi.). 

 Ser. 2.— Vol. III. 2 U 



