290 



E. C. FAUST. 



spermatozoa were similar in all respects to those obtained at 

 Woods Hole in August, 1913, from adult males of this species. 

 Because of their structure and specific reaction the author is 

 assured that all spermatozoa entering into consideration in the 

 data are mature individuals. 



The description of a mature spermatozoon becomes necessary 

 at this point. As far as the writer has been able to discover no 

 one has described a chromatic rod w r ith cytoplasmic sheath for the 

 mature spermatozoon of A nasa tristis. Paulmier's description and 

 figures show no such structure. Meek's figure for the ' ' penultimate 

 stage" of maturing spermatozoa of Stenobothrus viridulus shows 

 something of the nature of this chromatic rod (Plate III., Fig. 36). 



FIG. i. Mature spermatozoa, (a) Entire spermatozoa; (b) straight sperm- 

 head, the inner chromatic rod of this type was measured; (c) curved sperm-head, 

 a characteristic type not measured. 



The author's preparations agree with Paulmier's description of the 

 mature spermatozoon olAnasa tristis in having no middle piece dis- 

 tinguishable, so that the tail connects directly with the posterior 

 end of the head. The head has the chromatic elements com- 

 pacted into a long attenuated rod of nearly constant diameter 

 throughout its entire length. This chromatic rod is enveloped 

 by a cytoplasmic capsule. The latter is also attenuated, and has 

 a constant outer diameter. The length of the chromatic rod 

 ranges from 24^ to 36^ and the width from ^ n to f /JL. Although 

 the width is too minute for practical measurement, in general, 

 it seems to be proportional to the length. The cytoplasmic 



