ZOOLOGY AND BOTANY, MICROSCOPY. ETC. 785 



and the broken part turned downwards, the embryo proceeded to 

 develope itself normally, and at the same accelerated rate as after the 

 scraping of the shell. 



Dr. Gerlach gives directions for carrying out these experiments, 

 and describes a process by which the development can be watched 

 without injury to the egg, by substituting a piece of glass for a piece 

 of egg-shell. 



The above experiments completely disprove the wddely spread 

 opinion that those eggs, of which the shells are broken, cannot produce 

 an embryo. 



Early Development of Rana temporaria.* — Mr. W. Baldwin 



Spencer first discusses the fate of the blastopore, and comes to the 

 conclusion that, in Bana, as in Triton, it is transformed into the per- 

 manent anus ; between the two, however, there is this important 

 ditference that the latter shows no connection between the neural and 

 alimentary canals ; it is difficult to determine whether this connection 

 in Rana should be called a " neurenteric canal " ; it cannot be so if 

 we limit that term to its original significance in connection with the 

 inclosure of the blastopore, and when that orifice forms itself a means 

 of communication between the alimentary and neural canals. " Per- 

 haps, however, the term ' neurenteric canal ' may be applied to all 

 structures which allow of communication between the two canals, and 

 which itself, in subsequent development, closes up and disappears ; 

 using the term in this sense, one is clearly present and well-developed 

 in Bana." 



The author, secondly, discusses some points connected with the 

 early development of the cranial nerves. Before the closure of the 

 neural canal no development of nerves can be perceived ; in other 

 words, the neural ridge of the chick and of the elasmobranch appears 

 to be absent. The first appearance of the nerves is not in the form of 

 a direct outgrowth from the substance of the canal, but along certain 

 lines the cells of the nervous layer proliferate, and from these ])yo- 

 liferations the rudiments of the cranial nerves appear. The ganglia 

 are found to arise along the level of the lateral line continued on to 

 the head ; this curious mode of origin leads to the view that they 

 arise primitively as ganglia of the sense-organs of the lateral line of 

 the head ; in other words, their present position and nature is not 

 primitivo, but secondary. 



The mode of proliferation of nerves in Bana reminds the author 

 of the mode of origin of the lateral and pedal nerve-cords in the 

 Chitons, as recently described by Kowalevsky, and he thinks that the 

 embryonic neural sheath may be found to represent a more ancestral 

 condition than that which obtains in clasmobranchs and birds, re- 

 sembling as it does the arrangements seen in some invertebrates. 



Development of Motella mustela.f — Mr. G. Brook has investi- 

 gat^id the development of tliis fish with the following results. 



The eggs are pelagic with a large oil-globule to keep them floating. 



♦ Quart. Journ. Mier. 8ci.— Suppl., 1885, pp. 123-37 (1 pi.). 



t Journ. Linn. Soc. Lond.— Zool., xviii. (1885) pp. 2'J8 307 (3 pie.). 



