NOTICES OF SERIALS. 217 



of the new individual is not preceded by the phenomena of segmentation, as also 

 is the case with all true eggs. Therefore, their primitive formation, their develop- 

 ment, and the preparatory changes they undergo for the evolution of the new indi- 

 vidual, are all different from those of real ova. Another point is, these viviparous 

 individuals have no proper ovaries and oviducts. Distinct organs of this kind I 

 have never been able to make out. The germs are situated in moniliform rows, 

 like the successive joints of confervoid plants, and are not enclosed in a special 

 tube. These rows of germs commence, each, by a single germ-mass which sprouts 

 from the inner surface of the animal, and which increases in length and in the 

 number of its component parts from the successive formation of new germs by a 

 constriction -process, as already mentioned. Moreover, these rows of germs, which, 

 at one period, closely resemble in general form the ovaries of some true insects, are 

 not continuous with any uterine or other female organ, and, therefore, do not at 

 all communicate directly with the external world. On the other hand, they are 

 simply attached to the inner surface of the animal, and their component germs are 

 detached into the abdominal cavity as fast as they are developed, and then escape 

 outwards through a porus genitalis, exactly as is the case with the eggs of fishes. 

 Here, then, comes the important question — What interpretation shall we put upon 

 these reproductive parts— these moniliform rows of germs? Ignoring all existing 

 special theories relating to reproduction, the observing physiologist would be left no 

 alternative but to regard them as buds, true gemmae, which sprout from the inner 

 surface of the Aphis, exactly like the buds from the external skin of a Polype.'' 

 Dr. Burnett then gives the results at which other famous naturalists have arrived 

 upon this subject, and a discussion of the relations of the important conclusion at 

 which he has alone arrived ; and now — " The final question is, what is the le- 

 gitimate interpvetation to be put upon the reproductive phenomena of the Aphides 

 we have described? My answer to this has been anticipated in the foregoing re- 

 marks. I regard the whole as constituting only a rather anomalous form of gem- 

 miparity. As already shown, the viviparous Aphides are sexless; they are not 

 females, for they have no proper female organs — no ovaries and oviducts. These 

 viviparous individuals, therefore, are simply gemmiparous, and the budding is here 

 internal instead of external as in the Polyps and Acalephs ; it, moreover, takes on 

 some of the morphological pecularities of oviparity ; but all these dissimilar condi- 

 tions are ceconomical 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 many trees ; on the other hand, the 

 whole suit 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 sexual 

 and gemmiparous reproduction. Morphologically, they have, it is true, many points 

 of close resemblance ; but there is a grand physiological difference, the true percep- 

 tion of which is deeply connected with our highest appreciation of individual ani- 

 mal life. A true generation must be regarded as resulting only from the conjuga- 

 tion of two opposite sexes — from a sexual process in which the potential representa- 

 tions 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 prolongation by budding, or by 

 division, must always be within a certain cycle, and this cycle is recommenced by 

 VOL. I. Q 



