302 BUIvLETIN OF THE BUREAU OF FISHERIES. 



section of the sternum of the eighth thoracic segment. The divergent wing-like processes 

 in front of the annulus in the crayfish evidently correspond to the convergent wings, 

 which are the modified sternum of the seventh thoracic somite, and which, united with 

 the middle piece, form the elastic lips of the shield-shaped receptacle in Homarm 

 (St. xrii, fig. 4). 



The laying of eggs in the crayfish may not occur for some weeks after sexual union, 

 and as Andrews remarks, some protection such as the annulus affords is necessary, since 

 sperm can not long survive exposure to water. 



PAIRING HABITS IN THE LOBSTER. 



Both Boeck (24) and Fraiche (log) have referred to the union of the sexes in the 

 European lobsters as if they had witnessed the act, but the errors which they exhibit 

 tend to discredit their statements, however brief. Fraiche remarked that copulation 

 in both the common and Norwegian lobsters took place in fall (October and November), 

 and in the case of the former that it was extended into winter. "As with the crayfish, 

 the sexual act is accompUshed belly to belly, and so closely and firmly do they clasp 

 each other, that, if taken from the water at this period, it is with difficulty that they 

 can be separated." 



But the only reliable observations under this head have been made by Anderton (5), 

 of the Marine Department of New Zealand. The sexual act was noticed on a number 

 of occasions among the European lobsters kept under observation in small artificial 

 ponds. The general succession of events was as follows: Molting in early summer 

 (November and December), followed in the course of a few hours by coition between a 

 soft female and a hard male, and by the laying of eggs about two months after this 

 event. 



One of the female lobsters kept under observation by Anderton molted on Novem- 

 ber 2 1 , at 3 p. m., and lay for some time beside her cast shell. "Two hours afterwards," 

 to continue his account, "it was seen roaming round the pond and frequently approach- 

 ing the various shelters, returning regularly and fearlessly to a shelter containing a large 

 male. On approaching the entrance to this shelter the large claws were extended in a 

 direct line with the body and the antennae were thrust within the shelter. After a few 

 moments the rostrum of the male appeared, the fema,le meanwhile rapidly whipping 

 her antenna across the now projecting rostrum of the male, which in turn showed increas- 

 ing signs of excitement, the antennas being whipped very rapidly over the female in the 

 same manner. After an interval of perhaps a minute the male gradually withdrew 

 from his shelter, the female at the same time turning over on its back. Coition took 

 place at once, the act occupying only a few seconds, the male retiring at once to its own 

 shelter and the female into another. The following day both were observed to be living 

 in one shelter, and they continued to do so, on and off, for several weeks."" 



" In reply to certain specific questions regarding the pairing of lobsters, Mr. Anderton has kindly written imder date ot 

 August 21, 1910, as follows: " The female lobster after casting does appear to seek out a male as soon as the distressing effects of 

 molting have somewhat worn off. Male and female have frequently been observed living in one shelter for some days and even 

 weeks after coition. The act of coition is very brief, and will not occupy more than half to a whole minute. They copulate, as 

 you express it, " belly to belly," and head to head. The large chelse do not come into use during the act so far as I have observed. 

 The female volimtarily turns over almost completely onto her back, the excited male completing the process for her." 



