174 PROCEEDINGS OF THE ACADEMY OF [May, 



In the meantime von Baer (1835) reported an observation which 

 seemed to confirm Oken's view. He actually saw Lymncea auricu- 

 laria with -own penis inserted in its own female opening. Braun 

 (1888) isolated eggs of Lymncea auricularia in separate vessels and 

 raised the young snails which when they reached adult size laid 

 eggs which developed. Although this author had the snails under 

 observation for weeks and months at a time, he never was able to 

 confirm von Baer. Nevertheless, he did not doubt that von Baer was 

 correct in what he saw. The present writer has repeatedly isolated 

 eggs and had them develop into snails which laid fertile eggs, but has. 

 never witnessed a case of self-copulation. 



There is the alternative that must be disposed of : Can it be that 

 these eggs are not self-fertilized, but that they develop partheno- 

 genetically? This question cannot as yet be fully answered. To be 

 sure, normal parthenogenesis is unknown in mollusks, but direct 

 evidence on the case in Lymncea is lacking. The reduced number of 

 chromosomes in maturation of the sperm is small, six to eight, but 

 as yet the writer has been unable to satisfactorily imbed the eggs so 

 that they may be cut. As yet he has been unable to observe the 

 first cleavage figures. 



An examination of the reproductive organs of the snail will show 

 that there is no reason why self-fertilization should not occur. This 

 system is a complicated one in the lung-bearing mollusks, and 

 Lymncea is no exception to the rule. The eggs and sperm arise side 

 by side in a common ovitestis. When ripe both eggs and sperm pass 

 down a common hermaphrodite duct. Into this duct the albumen 

 gland opens, the function of which is to secrete around the egg a 

 thick coat of albumen. This is the substance which makes the eggs 

 so difficult to imbed. Past this point the duct divides into a thread- 

 like vas deferens with wider portion called the prostate gland, and 

 a thicker-Availed oviduct. The former leads finally to an invertible 

 penis just back of the tentacle on the right side of the animal, while 

 the oviduct opens somewhat to the exterior somewhat posterior to 

 the former with a narrow slit. Into the oviduct near its aperture 

 opens the duct from the so-called sperm receptacle, in which the 

 writer has never found sperm, but in which very often he has found 

 eggs. He hopes to deal with this matter at another time. 



The reason for describing in some detail the reproductive organs 

 of this animal is to make clear that there is every piece of mechanism 

 present to allow self-fertilization. If the eggs are not fertilized in the 

 upper part of the oviduct, they may be by self-copulation in the 

 lower part. 



