M. Ussow’s Zoologico-Embryological Investigations. 99 
or less detailed and accurate memoirs, which are chiefly de- 
voted to the embryology of the Decapoda. 
As early as the year 1841 Van Beneden published his inves- 
tigations on Sepiola Rondeletii*. In 1844 Kollikert enriched 
science with his well-known memoir on the development of 
various species of Decapod and Octopod Cephalopoda. Almost 
a quarter of century later (1867) EK. Metschnikoff t made known 
his investigations on Sepiola; and last year (1873) Ray Lan- 
kester published a short communication § on the development 
of Loligo. It seems scarcely necessary to enumerate the obser- 
vations of Cuvier||, Dugés{], and Delle Chiaje** relating to 
this subject, as in most cases they contain very unsatisfactory 
and erroneous TT statements as to the embryonal process. As 
it is impossible for me in this short summary to submit the 
results obtained by Van Beneden and Kélliker to criticism, 
and as in the following report upon my investigations I indi- 
cate the most important errors of those savants, I shall devote 
a moment only to the most accurate of all these memoirs, that 
of EK. Metschnikoff. 
We may regard as one of the greatest merits of the above- 
mentioned important memoir, which only relates to one 
species of Cephalopod, the first description of two germ- 
lamelle, and the more or less exact indication of the part 
they take in the subsequent formation of the different organs. 
Studying the development of Sepéola and the mode of forma- 
tion of the central nervous system, the intestinal canal, and the 
central organs of circulation solely in living embryos tt, with- 
out the aid of dissected preparations, must necessarily have 
caused Metschnikoff to miss many important facts, even with 
regard to the species investigated by him. As, moreover, 
from want of material, he was unable to trace the development 
of the ova, and especially their process of segmentation, this 
* “Rech. sur l’embryol. des Sépioles,” in Mém. de l’Acad. de Brux. xiv. 
+ Loe. cit. 
{ History of the embryological development of Sepiola (in Russian), 
1867. See Arch. fiir Naturg. 1868, Bd. ii. p. 130, and Arch. des Sci. Phys, 
et Nat. xxx. (1867) p. 186. The following citations apply to the complete 
Russian work. 
§ Ann. & Mag. Nat. Hist. 1873, no. 62, p. 81. 
| Ann. du Mus. 1852, i. p. 153. 
q Ann. des Sci. Nat. viii. p. 107, 1837. 
** Memorie, 2nd edit. p. 39, 1829; Notom. degli anim. invertebr. 1841, 
i. p. 85, pl. xxix. figs. 4, 5. 
t+ Kolliker, J. c. pp. 110, 111. 
t{ At least, in his memoir, Metschnikoff nowhere mentions that he 
studied sections, without which it is impossible to trace the formation of 
the intestino-fibrous layer, and to form a clear idea of the development of 
some organs. 
7 
