AND THE LOWER ANIMALS. 229 



of a nucleated cell — the germinal vesicle, which encloses 

 the germinal spot. The yelk, properly so called, or 

 viteUus, is but an accessory mass of matter for 

 alimentary purposes. The fundamental ovum is re- 

 produced, just as the monad, by fission; but this 

 phenomenon is alone determined by the intercom- 

 munication of the sexes. This act is necessary in 

 order to infuse a certain power, a peculiar prolific 

 force* into the germinal spot. In consequence of this 

 impregnation, the germinal vesicle disappears, the 

 germinal spot becomes contracted, and the first ger- 

 minal cell soon exhibits itself. At first, the latter 

 divides into two, then into four, and so on, the viteUus 

 itself undergoing, pari passu, the same multiplication. 

 It is in this way that Professor Owen explains the 

 segmentation of the yelk, and its transformation into 

 a mass of germinal cells, invariably endowed with the 

 prolific power which gave them birth, and which is 

 stored up within them. 



According to Professor Owen, it is invariably this 

 mass of germinal cells which, endowed with a special 

 force, constitutes the starting-point in the trans- 

 formation of a new being. In Mammalia, all ver- 

 tebrates, and in a great number of invertebrates, this 



Infusoria is now known, and that this organ, which plays so import- 

 ant an office ; is really an ovary, it is evident that many of the 

 theories based upon Schleiden's views must be revised, and that 

 it will be necessary to verify many of the facts which perhaps have 

 been accepted only in so far as they were founded on those views. 



# A spermatic force, a spermatic power. The arguments ad- 

 duced by Dr s Carpenter and Professor Huxley in opposition to the 

 views of their distinguished fellow-countryman, bear particularly on 

 the supposed existence of this special force. — Medico-Chirurgical 

 Beview, 1848 : " On the Agamic Eeproduction and Morphology 

 of Aphis." Transactions of the Linna?an Society, 1858. 



