AND MORPHOLOGY OF APHIS. 205 



substance seems to occupy the whole central part of the chamber ; but on carrying the 

 eye backwards, this clear mass is seen to be continuous with the two cords which I have 

 above described as entering the second chamber (PI. XL. fig. 3). 



The histological constitution of these bodies is at once sufficient to convince the observer 

 that they arc not ova, and I regard them as glandular masses wliich secrete the matter 

 of the clear cord-like bodies which descend into the second and third chamber. 



The ova themselves, or rather the rudiments of the future ova, are not always to be 

 seen with ease ; and if the epithelium of the lower part of the apical chamber has become 

 much altered, they cannot be detected : for they are visible exclusively in this part of 

 the chamber, of whose epithehal cells they are, as I believe, merely a modification. 

 However this may be, germinal vesicles and spots of all sizes intermediate between that 

 of the ovum of the second chamber and that of an ordinary epithelial cell are seen in 

 close contact with the jjarietes of the chamber. I have detected as many as six in tliis 

 position. When the chamber is subjected to compression they may be set free, and are 

 then seen to be surrounded by a zone of clear substance, the rudimentary vitellus. 

 Under similar circumstances, the "glandular bodies" may also be isolated; when they 

 present themselves as vesicles surrounded by a clear homogeneous substance, which is 

 frequently prolonged at their apical extremity. It is gradually dissipated, and the inner 

 sac set free by the action of water. 



I have not seen any ovarian ligament in the oviparous Aphis. 



The structure which I have described was wholly unexpected and new to me ; and I am 

 not aware that anything similar has yet been noticed in the ovaria of Insects*. I am 

 inclined to believe that the glandular bodies contribute directly to the formation of the 

 viteUus, because I have more than once seen cases, like that figured in PL XL. fig. 3, 

 where the clear cord-like body appeared to pass directly into the mass of the oviun. 

 There was always a widely open communication between the first and second, and 

 between the second and thii-d chamber; but the passage between the third and foui'th 

 was closed by the meeting of the epithelial lining. Does each ovum, as it is given oiF 

 from the ovary, and passes backwards, carry with it a gelatinous mass, the product of one 

 half of the glandular bodies, and only cease to be connected with these glands when it 

 has taken the third place ? 



Three caeca open into the dorsal side of the lower part of the vagina; of these the 

 anterior single one is the spermatheca, the posterior pair are the coUeterial glands 

 (PI. XL. fig. 1, m, n). 



The spermatheca («) is a sac with a narrow neck, dUated at its extremity, which opens 

 considerably in advance of the colleterial glands, while its enlarged end Kes between 

 them. The duct of the spermatheca has thick walls continuous with those of the vagina ; 

 but its dilated portion is thin, and has a yellowish colom-. It contains a multitude of 

 large filiform spermatozoa bent uj^on themselves, and is very tough and resisting. 



The colleterial glands (m) are subcylindrical, but are constricted inferiorly where they 



• Unless, as I am strongly inclined to suspect from Leydig's description, and from a hasty examination on mv own 

 part of the ovaria of Coccus, the corresponding chamber of that insect's remarkable ovaria presents a similar structure. 

 (See, however, the note which concludes this paper.) 



2 E 2 



