92 Dr. Burnett on the Development of Viviparous Aphides. 



rangement. Then again as to the constitution of each and both 

 being, on the whole, of nucleated cells, it may be said, that it 

 could hardly be conceived to be otherwise, for nucleated cells are 

 the elementary components of all functional organized forms; 

 and it may be added, moreover, that he knows little of the 

 highest physiology who has not learned that widely different 

 teleological significations may be concealed beneath isomorphic 

 animal forms. 



I have thus dwelt rather lengthily upon this point because I 

 think it is a vital one in our subject, and the possession of clear 

 ideas thereon will be found singularly conducive to our correct 

 appreciation of the whole class of anomalous phenomena under 

 discussion. But we will revert to the subject of Owen's hypo- 

 thesis. 



As to the chief point in this hypothesis, the continuation of 

 the primary germ-mass as a leaven, from brood to brood, it re- 

 quires butlittle thought to perceive that it is physically impossible. 

 I would first allude to Owen's statement, quoted above, that a 

 portion of the germ- mass is taken into the abdomen of the em- 

 bryo Aphis, and, as he thinks, assumes, without any change, the 

 position of the ovarium. By this- he refers, undoubtedly, to the 

 vitellus-looking mass I have described in my observations, and 

 according to which, also, it appeared to serve only as the nutritive 

 material out of which the digestive organs and the germs are 

 formed. Moreover, I feel quite sure that the germ-cells are new 

 cells formed in the abdomen, and not those derived from the 

 parent. 



But the point I wish to enforce is, that even admitting that 

 individuals B may contain an actual residue of individuals A, it 

 is clearly evident that this succession must stop with brood B ; 

 for these residual germ-cells which compose B in its earliest con- 

 dition are lost in the developmental processes, and the germs of 

 individuals C, which are found in B, are each, primarily, nucle- 

 ated cells formed de novo, as I have observed and above described. 

 With these observed conditions of development, it is impossible 

 for the individuals of the successive broods to inherit the original 

 spermatic force in the continuation of the original cells. 



The hypothesis of Owen, therefore, plausible and ingenious as 

 it may seem, does not appear to me to accord either with observed 

 facts, or with the soundest physiology of the reproductive pro- 

 cesses. I may here remark also, that his doctrine of Partheno- 

 genesis, based as it is upon the conditions of the hypothesis in 

 question, cannot, as such, be sustained, for the same reasons, and 

 all its phamomena would appear to find their solution either in 

 Stcenstrup's doctrine of "Alternation of Generations," so-called, 

 or in the conditions of true gemmiparity, — admitting, provision- 



