424 



GEOLOGICAL SURVEY OF THE TERRITORIES. 



on already copulated females, with filled uterine bags, whicli fact agrees 

 with what has been observed in Branchipus stagnalis. (In the latter the 

 claspers do not cross.) Slipping off of the female after having once been 

 clasped by the male, I could never observe in the normal red Eubran- 

 chipus. Therefore comparatively more muscular i)ower is required to 

 open the crossed chxspers, aud owing to this fact only has the copulation 

 a longer duration in the pale races 5 the same difficulty was noticed on 

 releasing the copulated female. Immediately after the clasping the post- 

 abdomen turns around to the ventral side of the female, the two nor- 

 mally crossed cirri-points enter the valvule simultaneously, spreading 

 open the same. 



The protruding trifold muscular apparatus, first observed and figured 

 by Dr. Heinrich Mtsche, in BranGhipus Grubei von Dybowsky (op. cit.), 

 is closely brought to the valvule, emptying through it (apparatus) and 

 not through the two cirri, the spermatic fluid evidently into the inner 

 uterine bag, where it meets with the revolving eggs. The claspers of 

 the male tightly pressing upon the anterior (upper) portion of the female 

 sack thus produce a gaping of the valvule. All this taking place in 

 an instant, the entering of the two cirri, however, is repeated several 

 times during the three or four minutes. A few jerks of the male post- 

 abdomen, apparently coincident with strained jerks of the male claspers 

 (and following right after) are necessary to free the two sexes. The 

 male slowly sinks to the bottom for several seconds, lays curved on its 

 back and repeats the post-abdominal jerks with protruded cirri and ap- 

 paratus. In this condition, and more so in clay- water, the seminal fluid 

 can be observed with an ordinary magnifying glass to ooze out of the 

 extensile apparatus and slowly flow over the sides of the curved abdo- 

 men. 



II. — Larval stages of Chirocephalus holmani Eyder. 



The single specimen of Ghirocephalus found in January, 1880, proved 

 to be Ghir. liolmani Eyder, being considerably larger, but agreeing in 

 general with the latter. On March 22, 1881, I found a very large and 

 deep x>ond between Glendale and Eidgwood, L. I., about three miles 

 from Maspeth, populated with Chirocephahis Jiohnani. So abundant 



were they that with every 



r^^^v^^M^'^'^'^^^ <3iP I brought up some 30 to 

 __c;ri5=«r ^ c « > ^ g^ specimens of both sexes. 



They were of a greenish 

 "^transparent hue with their 

 furca reddish pigmented. 

 The jjigment of the furca 

 was confluent and not gran- 

 ular. 



The males averaged 20"™ 

 in length and the females 

 about 18"^=". The stalked 

 eyes were of a beautiful 

 dark-red color. EiibrancMpus occurred sparingly together with them, 

 and now (in May, 1881), also a great number of a variety of Biaptomus 

 sanguineus Forbes^ and Lymnetis Gouldii Baird. 



Having observed them often in copulation in the aquarium, I can 



state that the latter is of very brief duration, and details relate to those 



of the normal red Eubranchipus, and principally the frontal tentacles 



do not come into play as auxiliary organs. 



The internal genital organs of the male are the same as those figured 



'Bulletin of Illinois State Labratory of Natural History No. 1. 



Pig. 48.- 



-A, male frontal tentacle of Oh. holmani 

 B, the samfe in male of H^tbranchipus vemalis. 



