ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 51 
The fact that in the one case the males are developed from 
pseudova resembling fully-formed true ova, and in the other from 
pseudova resembling imperfectly-formed ova, makes no essential 
difference in the analogy, but only demonstrates still more clearly 
the impossibility of drawing any absolute line of demarcation histo- 
logically between ova and buds. 
§ 6. Hypothetical Explanations of Agamogenests 
The majority of writers on the wonderful phenomena of Aphidian 
life have been content to state the facts more or less clearly ; but 
Morren, who has done this so clearly and philosophically, has in 
addition carelessly thrown out a hint of a mode of explaining them.. 
The agamic Aphis, he says, is a portion of organized tissue which 
individualizes itself :— 
“Suppose that vitality is sufficiently energetic to impress, on the 
tissue which individualizes itself, the form of the producing species,. 
and you have the generation of the Aphzdes. This energy becomes 
lost at the end of a certain number of generations, and a new impulse 
becomes necessary. It is that of the male. In my youth I might 
have adopted with pleasure such an hypothesis as this; but now I 
prefer to doubt: the facts which I have set forth are worth more than 
a theory.” 
The hypothesis is, however, to my mind, in no essential particular 
distinguishable from that hypothetical explanation which has been 
propounded by the author of the well-known work on “ Partheno- 
genesis.” Substitute for “energy of the male,” in the foregoing 
passage, “spermatic force;” and the difference between the two. 
hypotheses becomes evanescent. 
But this is a question of minor importance as compared with the 
value of the hypothesis in itself; and it is with regard to this latter 
point that I now propose to make a few remarks. 
Professor Owen’s views are, I believe, fairly stated in the following 
extracts from the work cited :-— 
“We find derivative germ-cells, and masses of nuclei like those 
resulting from the final subdivision of germ-cells, retained unchanged 
at the filamentary extremities of the branched uterus forming the 
ovaria of the larval Aphides.”—/ ¢. pp. 7, 8. 
“ According to my own observations, the germs are perceptible in 
the embryo Aphis, above the simple digestive sac, before any organs. 
have been formed for their reception. And with regard to the nature 
of the organs when formed, I may remark that the continuity of 
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