202 Papers from the Marine Biological Laboratory at Tortugas. 



This fertilization would result, according to Hertwig, in the production of 

 males: "The sex-determining capacity which is indicated in the female 

 by the formation of large eggs that are rich in yolk and small rudimentary 

 ones, in this case would be transferred to the male sex." 



Retzius ('06) described and figured the atypical spermatozoa oi Aporrhais 

 pes pelicani, Turritella terehra, Murex trunculus, Fusus despectus, and Buc- 

 cinum undatum. 



Popoff ('07) made a series of very careful and important observations 

 upon Paludina. He examined the seminal receptacles of a great number of 

 females at all times during the period of their sexual activity (May to 

 November). He found that any one of the following conditions may 

 obtain: (i) The receptacle may contain normal eupyrene and oligopyrene 

 spermatozoa; (2) it may contain normal eupyrene and degenerating oli- 

 gopyrene spermatozoa; (3) it may contain only eupyrene spermatozoa; 

 (4) it may be completely empty. Of the 476 females examined during the 

 whole period, in 176 cases the receptacle contained normal eupyrene and 

 oligopyrene spermatozoa; the proportion of the cases in this condition to 

 the total number examined at any one time showed a decided fall after the 

 period of greatest sexual activity was reached (July). The condition which 

 obtained in the next greatest number of cases (152) was the fourth, in 

 which the receptacle was empty, and here the percentages of cases increased 

 as the season advanced. In 89 cases the receptacle was found to contain 

 only eupyrene spermatozoa, i. e., the third condition; the percentage of 

 these cases fell during August and then held fairly constant. Finally, only 

 39 individuals were found to be in the second condition (normal eupyrene 

 and degenerating oligopyrene spermatozoa in the receptacle) ; here the 

 percentage of cases gradually increased until August and then fell in Sep- 

 tember. 



These facts indicated that the oligopyrene spermatozoa are shorter-lived 

 than the eupyrene. In order to ascertain this definitely, Popoff segregated 

 a number of females from the males immediately after copulation. From 

 time to time the seminal receptacles of several of these females were ex- 

 amined and as a result he was able to establish the fact that after 10 to 12 

 days the oligopyrene spermatozoa begin to degenerate, while this does not 

 occur among the eupyrene until after about 25 days. 



In addition to this, Popoff found both kinds of spermatozoa in equal 

 numbers in sections of the oviduct; only in the case of animals whose 

 receptacles contained no oligopyrene spermatozoa did he fail to find these 

 forms in the oviduct. This would indicate that the function of the oligo- 

 pyrene spermatozoa is to participate in the fertilization of the egg. His 

 results, however, in attempting to obtain eggs at the time of fertilization 

 were practically negative. In three eggs, which constituted the only clear 

 cases, Popoff found that the spermatozoa which had entered were eupyrene, 

 so that nothing could be stated with certainty concerning the function of the 

 oligopyrene spermatozoa. He thinks, however, if they may be said to have 



