ORGANS FOR SPERM-TRANSFER 291 
fate is to add on a lateral outgrowth (appendix masculina) which 
becomes the useful part of this organ when acting as a necessary 
part of the sperm transit apparatus. 
The duplication of all three organs, right and left, seems neces- 
sary in.as far as removal of one set leads to the lack of necessary 
mechanical support for the perfect functioning of the opposite 
set. 
The evidence is against the conclusion that the right and left 
openings of different receptacles upon different females are neces- 
sarily met by the males employing the stylets of one side rather 
than an other. In each case the male may by trial obtain the 
entrance of some one of the two stylets into the receptacle of the 
female. 
The extreme solidity of the shell of the stylets is to be correlated 
with the amount of force exerted by the male in making a water 
tight passage for the sperm from the deferent duct into the recep- 
tacle of the female. 
While all six organs are necessary for sperm transfer, most of 
them may be removed without preventing the males from carry- 
ing out many of the stages of conjugation that would normally 
lead up to sperm transfer. 
Many of the peculiarities of the form and structure of the trans- 
fer organs are demonstrated to be of use, or even necessary. 
The accurate interadjustment of the six organs is necessary for 
the perpetuation of the species. 
It is difficult to believe that in the evolution of Cambarus the 
increasing perfection of these organs could have been decisive 
in eliminating the less perfect organs. Astacus survives with 
more simple organs and the majority of genera of crayfish have no 
stylets at all. The perfection of the organs, characteristic of 
Cambarus may have been brought about from laws of change 
that it will require much experimentation to discover. 
JOURNAL OF MORPHOLOGY, VOL. 22, NO. 2 
