384 



succulent liquids this animal extracts from the tree on which it 

 lives, into this fatty liquid which is the nutritive material of the 

 germs. 



Omitting the curious and interesting details of the further his- 

 tory of the economy of these Insecta, as irrelevant to the point in 

 discussion, we will now turn to see what view we should take of 

 these processes, and what is their physiological interpretation. 

 In the first place, it is evident that the germs which develop 

 these viviparous Aphides, are not true eggs ; they have none of 

 the structural characteristics of these last, — such as a vitellus, a 

 germinative vesicle and dot ; on the other hand, they are, at first, 

 simple collections, in oval masses, of nucleated cells. Then, 

 again, they receive no special fecundating power from the male, 

 which is the necessary preliminary condition for the develop- 

 ment of all true eggs ; and, furthermore, the appearance of the 

 new individual is not preceded by the phenomena of segment- 

 ation, as is also the case with all true eggs. Therefore, their 

 primitive formation, their development, and the preparatory 

 changes they undergo for the evolution of the new individual, 

 are all different from those of real ova. 



Another point of equal importance, is, these viviparous indi- 

 viduals of the Aphides have no proper ovaries and oviducts. 

 Distinct organs of this kind I have never been able to make out. 

 The germs, as we have before seen, are arranged in moniliform 

 rows, like the successive joints of confervoid plants, and are not 

 inclosed in a special tube. These rows of germs commence, 

 each, from a single germ-mass, which sprouts from the inner 

 surface of the animal, and increases in length, and the number 

 of its component parts by the successive formation of new germs 

 by the constriction process as already described. Moreover, 

 these rows of germs which, at one period, closely resemble 

 in general form, the ovaries of some true Insecta, are not con- 

 tinuous with any uterine or other female organ, and, therefore, 

 do not at all communicate 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 thence escape outwards 

 through a Porus genitalis. 



