Papers from the Marine Biological Laboratory at Tortugas. 209 



upon either kind of spermatozoa except in a few instances where the egg- 

 membrane had been ruptured by the pressure of the cover-glass. In such 

 cases the eupyrene spermatozoa were strongly stimulated and swarmed 

 around the eggs in great numbers, but the apyrene spermatozoa in the 

 immediate vicinity of the eggs were not affected in the slightest. 



At the same time of the year the seminal receptacle of the female was 

 found to be quite swollen and full of a whitish mass. When some of the 

 contents was diluted with sea-water and examined it was seen that in 

 addition to a large number of oval granules only the eupyrene spermatozoa 

 were present. These latter were normal and very quickly became active. 

 Of a dozen females which were examined, not one showed a single structure 

 in the seminal receptacle which could possibly be identified as the remains 

 of an apyrene spermatozoon. The explanation of this phenomenon was 

 found only when sections of the seminal receptacle had been made and 

 studied. 



The uterus and seminal receptacle constitute that portion of the vagina 

 which lies just beyond the orifice of the oviduct, beneath the mantle. The 

 vagina itself is simply a groove running beneath the mantle, at its base and 

 on the right side, from the orifice of the oviduct proper to the foot; it corre- 

 sponds to the genital groove of the male. Just below the orifice of the 

 oviduct, the upper fold of the vagina is much broadened and thickened and 

 is covered by the lower wall which is correspondingly broadened, forming a 

 contractile sheath or mantle. This thickened portion of the vagina is the 

 true seminal receptacle; it is a gland comprised of a large number of con- 

 voluted tubules lined with a secretory epithelium. The space between the 

 seminal receptacle and its sheath may be spoken of as the uterus. Lying 

 around the seminal receptacle in a semicircle is the main portion of the 

 nidamental gland ; one branch of the latter extends down along the vagina 

 for a certain distance. The ducts of the nidamental gland open into the 

 vagina, just below the seminal receptacle. Further on down, and at the 

 point where the lower branch of the nidamental gland ends, is the opening 

 into the vagina of a large diverticulum, the bursa seminalis. Beyond this 

 point the vagina traverses the foot as an unmodified groove. 



In the sections mentioned above, it was found that there was a dense 

 detritus in the uterus composed of eupyrene and apyrene spermatozoa. 

 Apyrene spermatozoa with relatively few eupyrene scattered amongst them 

 formed the inner portion of this detritus. Segregating themselves from the 

 apyrene spermatozoa, the eupyrene had moved for the most part to the 

 periphery of the detritus. A clear homogeneous substance separated them 

 from the apyrene spermatozoa. Other eupyrene spermatozoa had moved 

 on into the tubules forming the seminal receptacle and had there arranged 

 themselves with their heads against the outer surface of the epithelial cells. 

 Here they were undoubtedly receiving nourishment, as was shown by the 

 vacuoles which had taken the place of the distal granules of the secretory 

 cells. In five series of sections no traces of apyrene spermatozoa were 

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