206 Papers from the Marine Biological Laboratory at Tortugas. 



been tinged to a purple color by the addition of a small quantity of a con- 

 centrated solution of gentian violet. The gentian violet was added to 

 provide a nuclear stain for such structures as had not retained the iron 

 haematoxylin ; it gave a differential stain to the spheres and thus proved to 

 be of considerable value. This stain has been used subsequently by othec 

 workers in this laboratory with fair success. Sections of the uterus and the 

 seminal receptacle were stained in the same way. 



Smears from the testis, the vas deferens, and the seminal receptacle were 

 prepared by making thin films of the contents of those organs diluted with 

 sea-water. The films were allowed to dry over osmic vapor, were washed in 

 fresh water, and then stained with Delafield's or iron haematoxylin. 



Sea-water was found to be the best artificial medium for studying the 

 living cells. The contents of the testis or sperm-duct were mixed with sea- 

 water and then a drop of the mixture was placed on a slide and surrounded 

 by a complete ring of glycerine-gelatine. In this way, a cover-glass placed 

 upon the drop was not only supported, but it was also given enough rigidity 

 to permit the use of an oil-immersion lense. If care were taken to see that 

 the ring of glycerine-gelatine was unbroken, practically no evaporation of 

 the mixture would take place. Under these conditions the various cells of 

 the testis would remain alive for at least 2 hours. Sometimes methylene 

 blue was used as an intra vitam stain, but this was found to be quite unneces- 

 sary and to cause an earlier breakdown of the cells than would otherwise 



occur. 



OBSERVATIONS. 



ADULT SPERMATOZOA. 



The eupyrene spermatozoa of Strombus bituberculatus resemble in general 

 those of other Prosobranchs. They are relatively short when compared 

 with the spermatozoa of Fasciolaria, Littorijia, or Neritina. The perfo- 

 ratorium is short and conical, the head thick and spindle-shaped (fig. 7). 

 The head and the middle-piece, which is very slender and passes almost 

 imperceptibly into the tail, constitute about half the total length of the 

 spermatozoon. 



In marked contrast to them stand the apyrene spermatozoa (fig. 6). 

 The term "worm-shaped" can in no wise be applied to these, as they are 

 totally different from the oligopyrene spermatozoa of Paliidina. They were 

 first described by Brock ('87) in the case of S. lentiginosus and again more 

 recently and in some detail by the present writer ('12) in the case of 5". 

 bituberculatus. While Brock's brief description is correct as regards the 

 general facts, his figure of the adult apyrene spermatozoon is not in accord 

 with the facts as they have been observed by the present writer in S. 

 bituberculatus, and there is no reason to suppose that any very great vari- 

 ation occurs between the apyrene spermatozoa of the two species. In 

 their structure, the apyrene spermatozoa of 6". costatus are identical with 

 those of S. bituberculatus, the only difference being in their respective lengths. 

 Apparently Brock did not fully understand the structure of the undulating 



