192 RELATIONS OF OVA AND GEMMAE. 



nal, strictly corresponding to those of true females 

 neither ovaries nor oviducts. 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 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 a process of constric- 

 tion. These rows of germs, indeed, closely resemble, in 

 general form, the ovaries of some insects, but they are not 

 continuous with any uterine or other female organ ; 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 out- 

 wards through &porus genitalis. Farther, he states that 

 the germs have none of the structural characteristics of 

 true ova such as a vitellus, or a germinal vesicle and dot ; 

 on the other hand, they are at first simple collections, in 

 oval masses, of nucleated cells, and the appearance of or- 

 ganization is not preceded by the phenomena of segmenta- 

 tion. But he admits that soon after their formation " a 

 vitellus-looking mass is formed in connection with each."* 

 Cams takes a somewhat similar view ; Leydig again main- 

 tains that the germs of the Aphis do possess a germinal 

 vesicle and macula, and that they appear to have in other 

 respects the same internal structure as the ova. Mr. Lub- 

 bock, while admitting that he has not been able to detect 

 these parts, appears inclined rather to ascribe this to their 

 indistinctness in the eggs of insects generally. ( Huxley and 

 Leuckart arrive at the same conclusion, that histologically 

 there is no difference in the germs of the oviparous and 



* Dr. Burnett's observations are given in Ann. and Mag. of Nat. Hist., 

 Aug., 1854, in Silliman's American Journal, Jany., 1854, and in his con- 

 cluding note to his Translation of Siebold's Compar. Anatomy. 



f Philos. Transact., 1857, p. 95. 



