144 Miscellaneous. 



ments. The embryonic cells, on the contrarj% multiply by division, 

 to form a cellular zone of increasing extent, which finally, under 

 the form of a cellular vesicle, will enclose the central mass of nutri- 

 tive matter. From that time the blastoderm is formed. 



It results from this that the large cell, which M. Gerbe has re- 

 garded as representing the body producing the vitellus, is really the 

 entire Q^g,, — that the egg of the Saccidinoi cannot be compared to 

 the egg of birds, since it is impossible to distinguish in it anj- parts 

 corresponding to the yolk and the cicatricula, — that the polar cell, 

 which has been considered to represent the germ, is analogous to 

 the jn'otoplasmic cord of the egg of the Ancliorellce, — and that this 

 cell separates from the matxire e^g, and remains in the ovary to be- 

 come divided there and give origin to new eggs. 



It is very evident, also, that no comparison can be established 

 between the vitelline body of the eggs of some spiders, or of certain 

 Myriopods, and the cell-nuclei of the double egg of the Sacndino'. 

 The vitelline bodj- of the egg of the sjiiders, of which MM. von 

 Wittich, von Siebold, and V. Cams have studied the constitution and 

 the mode of formation, and of which M. Balbiani has proved the 

 existence in the Myriopods, never presents the characters of a vesicle 

 or of a cell-niicleus. This body, far from being general in all 

 the animal series, does not exist in all the Araucida, nor even con- 

 stantly in the same species of Myriopod, such as GeopMlus simplex: 

 the signitication of this accidental element of the egg remains still to 

 be determined.^Co?>!2:>^es Eendus, tome Ixix. November 29, 18G9, 

 pp. 114G-1151. 



Food of Oceanic Animals, 



Dr. Wallich complains that I omitted to notice what he had pub- 

 lished on the subject. I must confess that I overlooked it. 



In his ' North- Atlantic Sea-bed' (p. 131), he says that it may be 

 asked " under what other conditions than exceptional ones can 

 marine animal life be maintained without the previous manifesta- 

 tion of vegetable life, as must be the case if it exists at extreme 

 depths'?" and he answers this inquiry by submitting that "in the 

 majority of the marine Protozoa, as, for instance, in the Foramini- 

 fera, Polycystina, Acanthometrae, ThalassicoUidaej and Spongidte, the 

 proof of these organisms being endowed with a power to convert 

 inorgaJiic elements for their own nutrition rests on the undisputed 

 power which they possess of separating carbonate of lime or silica 

 from waters holding these substances in solution." But surely this 

 is not a satisfactory answer to the inquiry. A limpet sejjarates 

 carbonate of lime from sea- water; but it cannot be assumed that 

 this animal (which is well known to be a vegetable-eater) has also 

 the power of converting other inorganic substances for its own 

 nutrition. Foraminifera, as well as Amoebae, are usually considered 

 animal-eaters, feeding by means of their pseudopodia or expansions 

 of the sarcode. As regards sponges, we find, from Dr. Bowerbank's 

 Monograph (vol. i. p. 122), that, in the greater number, their nutri- 



