38 



ration'; and affirms that " no true ovary has been discovered 

 in the larval and larviparous Aphides, but that the germs, 

 as soon as they are perceptible, are situated in organs which 

 must be regarded as oviducts and uteri." (p. 112.) Accord- 

 ing 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 the ovarian tubes with the 

 oviducts in all insects is such as to render the negation of 

 the term ( ovary' to those two bodies from which the slender 

 extremities of the eight oviducal and uterine tubes proceed 

 in the larval Aphis, to say the least, quite arbitrary. My 

 examinations agree with those of Siebold, in determining 

 scarcely any appreciable difference between the ovaria of 

 the oviparous and those of the viviparous females. The 

 contents of the ovarian tubes differ, inasmuch as they con- 

 tain oval masses of granules or nuclei, comparable to the 

 germ-mass in its state of minutest subdivision, in the virgin 

 aphides, and not ova with the germinal vesicle as in the 

 oviparous females. The most marked and essential di- 

 stinction, however, between the generative organs of these 

 two kinds of female is the multilocular form of the uterus 

 and simple vagina in the viviparous one, and the super- 



those individuals in other classes that contain ' potentially ' the higher 

 form, and generate it by gemmation, than to restrict it to those that are 

 actually themselves metamorphosed into such form, which metamor- 

 phosis is, after all, but a minor degree of metagenesis. Throughout 

 Prof. Steenstrup's essay we meet indeed with instances where Nature, 

 as it were, compels him so to use the Linnsean term or an equivalent ; as 

 e. g. where speaking of the larval Medusse he writes : " But there is also 

 a most essential difference between the young fry and the full-grown 

 animal." " Let us now trace these young Medusae further" (p. 14), 

 meaning the individual or ' larva* in the mask of the ' planula' of Sir 

 J. G. Dalyell. "This polypiform animal, which we shall afterwards 

 consider as a pedunculated Medusa." (p. 15.) In what respect is it less 

 erroneous, on Prof. Steenstrup's own argument, to call this Scyphistoma 

 ' a pedunculated Medusa' than a ' larval Medusa ' ? 



