DEPARTMENT OF MARINE BIOLOGY. 211 



tozoa takes place; this is probably accomplished by the clumping of the 

 apyrene spermatozoa and the very active movements of the eupyrene away 

 from the former. Third, the eupyrene spermatozoa are stored and nourished 

 in a specialized portion of the oviduct, the seminal receptacle. Fourth, the 

 apyrene spermatozoa never reach the seminal receptacle, but instead they 

 pass into a large, blind sack, the bursa seminalis, where they may be found, 

 together with eupyrene spermatozoa, in all stages of katabolism. Eventually 

 the entire mass becomes encapsulated by a secretion from the walls of the 

 sack and is thrown off. It is probable that during copulation the ejaculate 

 is placed in the bursa seminalis, although in several instances when the latter 

 was full, a recent ejaculate was found lying free in the mantle cavity. 



While these facts give no positive indication of the function of the apyrene 

 spermatozoa, they eliminate the possibihty of a direct participation by them 

 in fertilization. It is believed, however, that they may play an accessory 

 role in fertilization or may aid in the final disposition of the eupyrene sper- 

 matozoa. The most fruitful way of attacking this question is by an experi- 

 mental investigation of the behavior of the two kinds of spermatozoa. That 

 much information concerning the phenomenon of fertilization can be gained 

 from this kind of research has been amply shown by the work of Lillie^ and 

 Loeb.^ In addition to that broad field of investigation, the problem here is 

 unique in that, in the case of the apyrene spermatozoa, we are dealing with 

 non-nucleated cells, and any information which may be gathered concerning 

 their behavior will doubtless have an important bearing upon cellular structure 

 and physiology, 



A set of preliminary experiments clearly established three of four general 

 facts which must be reckoned with. The first of these is that the two kinds 

 of spermatozoa of Stromhus withstand a far greater range of changing con- 

 ditions than do the spermatozoa of Nereis or Arbacia. Thus, for instance, 

 when placed in a mixture of equal parts of normal sea-water and sea-water 

 charged with CO2 from a "sparklet" bottle, their behavior is practically the 

 same as in normal sea-water, except that the reactions take place more slowly. 

 When placed in undiluted sea-water charged with CO^, which has been allowed 

 to stand for 8 to 10 minutes until the bubbles cease to arise, they still retain a 

 slow degree of activity. The apyrene spermatozoa show remarkable powers 

 of recuperation after exposure to solutions hypotonic to sea-water. 



Wlien placed in 90 per cent sea-water, that is, in 90 parts of sea-water mixed 

 with 10 volumes of distilled water, the apyrene spermatozoa act normally after 

 a slight stimulation. When the percentage of sea-water is further reduced, 

 water is absorbed by the cells, and these become greatly swollen, distorted, 

 and immobile. When, by evaporation, the concentration of the salts in such 

 a culture is increased to within 10 per cent of that of normal sea-water, there 

 ensues a loss of water from the cells and the apyrene spermatozoa resume their 

 normal appearance and activity. 



By a series of experiments it was found that the apyrene spermatozoa would 

 recover even after being subjected to 60 per cent sea- water. At greater dilu- 

 tions than that, however, they were usually permanently impaired. It was 

 also found that the apyrene spermatozoa would withstand a 10 per cent 

 increase, by evaporation, in the concentration of sea-water, but the limits 

 from which they would recover in this direction have not been determined. 

 The eupyrene spermatozoa also recover after exposure to certain degrees of 

 dilution and concentration of sea-water, but their range is not so great as that 

 of the apyrene. 



ijourn. of Exp. Zool., vol. 14, 1913; also. vol. 16, 1914. -Ibid., vol. 17, 1914. 



