OF ARTS AND SCIENCES. 45 



" With such data, and which are, indeed, all we possess, we ask, 

 What is the physiological signification of this fissurating process in 

 cells ? 



" To this I would reply, that it seems to be simply an expression of 

 a vitalizing act, — a means by which cell-particles are extended or 

 reproduced on the one hand, and, on the other, by which crude mate- 

 rials of organized matter are kneaded or worked over for the forma- 

 tion of tissue in distinct individual beings. 



" Thus with simple cells, with the unimpregnated ovum, and with 

 the sperm-cell, this process occurs, leading to a mere reproduction or 

 multiplication of the cells, and which may continue to a greater or 

 less extent ; while, on the other hand, with the impregnated ovum,, 

 these processes, although physically the same, are directed from the 

 fecundating act towards a definite end, that is, the formation of tissues 

 which compose a new being. 



" In this connection, I may. well allude to those anomalous phenome- 

 na, the successive reproduction of individuals without the aid of the male 

 influence, as occurs with the Aphides. The general character of this 

 form of multiplication of individuals is well known in science ; but 

 what I wish to insist upon now is, that these phenomena, as I have re- 

 cently studied them, have nothing antagonistic to the doctrines of cells 

 just advanced, for the so-called eggs of the viviparous Aphides, and 

 which develop without the aid of the sperm, are, in my opinion, not 

 true eggs, but are rather huds, and therefore development here occurs 

 by a kind of internal germination. But this subject of the develop- 

 ment of Aphides in its details, as I have recently enjoyed the oppor- 

 tunity to successfully study it, I intend to present at the next meeting. 



" Cell segmentation, therefore, is a vital act of cells as organic par- 

 ticles, and is primary instead of secondary in the grand acts of true 

 generation. 



" This subject, important as it is in itself, has a wide physiological 

 beari/ig. If such phenomena invariably attend the production of a 

 new individual form from a true egg, can there be, as has recently 

 been advanced by several physiologists, animals composed of only a 

 single cell ? To this question the answer would be in the negative ; 

 and such forms would seem to me no more worthy to be regarded 

 as true animals, than would be the resultant products of segmented 

 epithelial cells. 



" On the very lowest confines of the animal kingdom there are. 



