164 report — 1859. 



contents of the vesicle as described. The extremity of the sperraatheca may be 

 found at first in the blind appendage; then it is broken up and conveyed into the 

 bladder, but often the principal portion of it (three or four inches) will be found 

 hanging out of the animals, after the reciprocal approach. The ova then are 

 impregnated in the matrix of each animal by the influence of its fellow ; they 

 receive a strong coating of albumen from the ovary, and investing membranes or 

 shelly coats from the matrix itself, where they are afterwards found fully developed 

 in its folds. 



In a strong muscular sac, evertile also, exists, as is well known, an organ of exci- 

 tation in the shape of a calcareous dart or spear. This is formed from the secretion 

 of the two fimbriated organs, near the base of the sac : I have found that their 

 milky product effervesces with a little acid ; besides, they only exist where the dart is 

 employed. I shall not describe this curious instrument, as it has been often noticed ; 

 but may mention that Helix virgata has two sacs and two curved lances, like minia- 

 ture elephants' tusks. In Carocolla lapicida the secreting organs are only two 

 long simple caeca. Cuvier does not figure, in the Helix pomatia, the long appendage 

 of the vesicle, so remarkable in Helix aspersa. In Helix nemoralis the neck of the 

 vesicle is very long, its appendage originating higher up, and floating at the end, and 

 all these parts very dark with pigment. Ctausilia has a short appendage and no 

 dart : the slugs have neither. 



It is curious that the hollow conical base of the dart, marked by its ridges, from 

 twelve to eighteen, is often found after the sexual approach in the neck of the vesicle ; 

 I suppose accidentally. Another curious fact is that the dart itself, though it may 

 be seen sticking from the flank of the animal, or fallen to the ground, yet generally 

 is found in the interior of the animal, amongst the fimbriae, by the side of the 

 matrix, or often where the vas deferens joins the ovary. Why this is, seems 

 doubtful ; my theory is that the recoil of the animal into its shell when struck may 

 cause the dart to enter so deeply, and that it has no other function than that of a 

 stimulus. 



It may be seen, then, that each snail reciprocally impregnates and is impregnated. 

 There is a transference of spermatozoa, possibly of ova, though I think not in Helix, 

 though so in Limncea. In the sexual congress the male organ is found, finallj', 

 with its opening to that of the vesicle and its appendage, but at first closely applied 

 to that of the matrix, with the spermatheca a little inserted. Does it supply the 

 matrix first, and then the vesicle or pouch of reserve ? or does (as is the case in some 

 annelides for instance) the spermatic fluid of one individual occasionally impregnate 

 itself by the aid of the second ? I think not ; for what would then be the use of the 

 intervening duct ? Once I found the penis half-exserted and lying in its own vaginal 

 cavity. This I consider accidental, and no proof of self-fertilization. I have given 

 the anatomy correctly ; perhaps some one cleverer at an enigma may give a better 

 solution with respect to the physiology. 



We have noticed the spermatozoa of Helix and Nerilina (some species of which 

 appear to be hermaphrodite) to put on the forms of ordinary cells by endosmosis. 

 In the vesicle and testis of Helix are often found immense numbers of extremely 

 active animalcules, having much the appearance of columnar cells. If we add water, 

 they quickly become tadpole-like in form, are still more active, and finally globular 

 and motionless; the endosmosed spermatozoa cannot be distinguished from the 

 moving cells or animalcules, if they are such, and both may resolve into globules; 

 but we only mention this as a curious correspondence. How the spermatozoa are 

 finally disposed of, we are not aware ; we suppose by solution. They are in Helix 

 from the twentieth to the thirtieth of an inch in length, the vitellus about the isVo^, 

 so that the theory of their entering it can scarcely be held in this instance. 



Limncea staynalis has similar organs, hut no appendage to the penis, and conse- 

 quently no spermatheca. It is remarkable that here the vas deferens divides and 

 goes both to the matrix, through a tortuous ciliated duct, into which the ovary also 

 opens above, and likewise to a second canal, analogous to the false duct of the Helix, 

 but here not communicating with the matrix, but communicating, as well as the 

 tortuous ciliated duct, with the ovary above ; and it would appear that both ova and 

 spermatozoa may be conveyed by the second canal through the reservoir at the 

 bottom, through the interventional duct, and so to the intromittent organ or penis 



