60 EDWARD DRANE CRABB. 



separate the ova from the spermatozoa. Moquin-Tandon ('55) 

 in speaking of the hermaphroditic Gastropoda in general, says 

 that the eggs are caused to fall into the uterus by escaping between 

 the lips of the longitudinal groove (presumably in the hermaphro- 

 dite duct). He infers that this mechanism prevents sperms from 

 entering the uterus as well as eggs from entering the vas efferens. 

 Lacaze-Duthiers ('99) states that in Ancylis it is possible to find 

 sperms in the upper part of the uterus ; but if they are found there 

 it is an exception. He advances the theory that while a snail is 

 functioning as a male, its oviduct is closed and thus prevents the 

 entrance of sperms. Likewise while the animal is functioning as a 

 female only the female conduit is open ; therefore no special struc- 

 ture is necessary to insure separation of eggs and sperms. Owing 

 to the continual presence of sperms in the hermaphrodite duct and 

 ovotestis, this idea is wholly untenable for L. s. appressa. He 

 refers to a statement made by Dubreuil, 1873, that in Helix the 

 ova fall into the oviduct while the sperms pass on down the male 

 part. It would seem that any opening through which an ovum 

 could fall would certainly admit sperms which are very much 

 smaller and motile. 



I have not been able to find any special device for separating 

 the eggs from the spermatozoa in L. s. appressa, but in sectioned 

 tissue I have found ova which had passed through the male con- 

 duit during copulation and had been injected into the sperm re- 

 ceptacle along with the sperms, and I have commonly found 

 masses of sperms in the albumen of the eggs of L. s. appressa and 

 L. pahistris which were isolated as embryos and kept in strict 

 isolation. Wierzejsky ('05) found masses of sperms in eggs of 

 Physa fontinalis. Of three L. s. appressa sperm receptacles fixed 

 at the time of copulation, one contained several ova. Since these 

 ova had no albumen around them, it is clear that they passed from 

 the acting male into the sperm receptacle of the acting female. 

 Things have often been seen in the albumen of sectioned eggs of 

 L. s. appressa which probably were pieces of single sperm tails 

 and heads. From the foregoing account it is apparent that sper- 

 matozoa are usually passed out with ova and subsequently en- 

 veloped in the albumen by the egg membrane, and that ova some- 

 times pass out through the copulatory organ and are injected into 

 the sperm receptacle along with the spermatozoa. 



