76 Dr. Burnett on the Development of Viviparous Aphides. 
If in this discussion of some of the highest relations of physi- 
ology, we have not wandered too far from our subject proper 
which we have thereby sought to illustrate indirectly, we will re- 
vert to the thread of its discourse for a few concluding remarks. 
The final question now is, what is the legitimate interpretation 
to be put upon the reproductive phenomena of the Aphides we 
have described? My answer to this has been anticipated in the 
foregoing remarks. I regard the whole as constituting only a 
rather anomalous form of gemmiparity. As already shown, the 
viviparous Aphides are sexless ; they are not females, for they have 
no proper female organs, no ovaries and oviducts. ‘These vivipa- 
rous individuals, therefore, are simply gemmiparous, and the bud- 
ding is here internal instead of external as in the Polyps and 
Acalephs ; it, moreover, takes on some of the morphological pe- 
culiarities of oviparity, but all these dissimilar conditions are eco- 
mical and extrinsic, and do not touch the intrinsic nature of 
the processes concerned therein. 
Viewed in this way, the different broods of Aphides cannot be 
said to constitute as many true generations any more than the 
different branches of a tree can be said to constitute as maby 
trees; on the other hand, the whole suite from the first to the 
last constitute but a single true generation. I would insist upon 
this point as illustrative of the distinction to be drawn between 
serual and gemmiparous reproduction. Morphologically, they 
have, it is true, many points of close resemblance ; but there 1s 4 
grand physiological difference, the true perception of which 3s 
deeply connected with our highest appreciation of individual an- 
imal life.* A true generation must be regarded as resulting only 
from the conjugation of two opposite sexes—from a sexual pro- 
cess in which the potential representations of two individuals are 
united for the elimination of one germ. This germ-power may 
be extended by gemmation or by fission, but it can be formed 
only by the act of generation, and its play of extension and pro- 
longation by budding, or by division, must always be within 4 
certain cycle, and this cycle is recommenced by the new act of 
the conjugation again of the sexes. 
In this way, the dignity of the ovum as the primordinm of all 
true individuality is maintained; and the axiom of Harvey, omné 
vivum ex ovo, stands as golden in physiology. The buds may 
put on the dress and the forms of the ovum, but these resemblances 
are extrinsic and in fact only an inheritance from their great 
predecessor. 
* Tn this view as well as in several others herein discussed, I am pleased to Say 
that I have the support of so learned a physiologist as Dr. Carpenter. See his Re 
view “On the development and Metamo of Zoophytes” in the Brit. and For- 
eign Med. Chir. Rev., 1848, i. p. 183; and “On Reproduction and Repair” in Ibid. 
1849, ii, p. 419. 
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