274 NOTES AND MEMORANDA. 



• Comptes Rendus ') at p. 138, lias now been publislied in Professor 

 Lacaze-Duthiers' ' Archives,'* wliere it occupies thirty-two pages. 



B. INVEETEBRATA. 



Formation, Fructification, and Division of the Animal Ovum. — 

 This subject is treated of in two papers by Oscar Hertwig,f each 

 illustrated by three plates. He works out very fully for Echino- 

 derms, Worms, Coelenterates and Molluscs, the important questions of 

 the fate of the germinal vesicle, the formation of the " polar cells," 

 the precise phenomena attending impregnation, and the mode of forma- 

 tion of the first cleavage-nucleus of the fertilized egg. His results 

 are for the most part confirmatory of his former observations, J and are 

 briefly as follows : — 



Before impregnation, the germinal vesicle becomes profoundly 

 altered ; its membrane disappears, and itself assumes a spindle form, 

 with the usual radiation of granules from its poles. It then approaches 

 the periphery of the egg, and one end of it passes into a small pro- 

 minence on the surface of the latter. The spindle then divides in the 

 usual way, one part remaining in the egg proper, the other in the 

 prominence, which now becomes separated off as the first polar cell. 

 The same process is gone through once more, and another polar cell 

 formed. The portion of the nucleus still left in the egg now undergoes 

 a change, becoming converted into a rounded body — the female pro- 

 nucleus — surrounded by radiating granules. At about this time, or 

 somewhat before, fertilization takes place, usually a single sperma- 

 tozoon making its way into the vitellus, whereupon its tail undergoes 

 absorption and its head is converted into a body — the male pronucleus 

 — closely resembling the female pronucleus. The two pronuclei travel 

 towards one another, coalesce, and produce by this process of conjuga- 

 tion, the first cleavage-nucleus of the impregnated egg. 



Digestion of Albuminoids by Invertebrata. — The researches 

 of Dr. Fredericq have been directed to Annelids, a cestoid Worm, 

 Molluscs, Ascidians, a Bryozoon, an Echinoderm, a Ccelenterate and 

 some Sponges. He treats the digestive organs of the animal, if they 

 are large enough to be isolated, with alcohol. If the animals are too 

 small he places a considerable number of them entire in the alcohol, 

 which coagulates the albuminoid bodies, sparing the ferments. The 

 objects thus treated are dried and pulverized, and the powder should 

 contain the ferments. To distinguish them, one part of the powder is 

 infused in distilled water, another part in water acidulated with 

 muriatic acid, and a third with water alkalized by carbonate of soda. 

 A piece of fibrin placed in the different liquids, heated to 40°, indi- 

 cates by its solution or resistance the presence or absence of ferments 

 analogous to pepsine or thrypsine. 



The general result was found to be that the transformation of 

 aliments is effected in the Invertebrata by digestive ferments analogous 

 to those of the Vertebrata.§ 



* Vol. vii. (1878) 251. 



t 'Morphol. Jahrb.,' iv. (1878) 156 and 177. 

 X See Balfour, in 'Quart. Journ. Mikr. Sci.,' xviii. (1878). 

 § 'Bull. Acad. Roy. Sci. Belg.,' xlvi. (1878); 'Rev. Internat. des Sci.,' iii. 

 (1879) 80. 



