ANATOMY OF STYLETS OF CAMBARUS AND ASTACUS. 83 



the end of the canula and represents the edge of the external 

 mass along the side of the groove, but before the orifice at the 

 base of the spiral is reached the shelf disappears and does not 

 continue on as part of the lip of the orifice. 



Within the minute tubule a small number of sperms were seen. 



The use of these organs in the processes of sperm transfer 

 was seen to be the same as in C. affinis. In brief the phe- 

 nomena were : The hooks of the third legs hold the male 

 firmly to the female. The male holds the claws of the female. 

 The first and second stylets are locked together and the fifth 

 leg is crossed. The pleopods are swung back and forth. The 

 second stylet glides a millimeter or so up and down the first, 

 with its wedge in the groove. Occasionally jerks of the base of 

 the abdomen make slight hammering thrusts of the tip of the 

 stylet-complex. While both stylets present their tips to the slit 

 of the annulus it seems difficult for both to enter at once since 

 the slit is median and not transverse. The exopodite of the 

 second stylet shows some slight twitching movements. The 

 female pleopods of the first somite extend over the annulus and 

 touch the setose palp of the stylet. On removing such a con- 

 jugating male and placing the fifth leg across to support the 

 locked stylets, sperm issued from the hole at the tip of the 

 canula and in a few minutes sperm came out of the tips of both 

 papillae. In separating a pair one stylet was very firmly 

 fastened in the annulus and tended to pull the annulus away 

 with it. This stylet had shoved the annulus up into the body of 

 the female as far as possible. This attached stylet was on the 

 same side as the crossed fifth leg. 



CambariLS MonteziivKZ is a representative of the subgenus Cam- 

 barelliis from Mexico, and should present, in some respects at least, 

 a more nearly ancestral state than the above species. 



Nothing is known of the conjugation habits, as the species is 

 known only from preserved specimens. The male has two hooks 

 on each side, and presumably both are used as is the one in C. 

 diogenes. These hooks (Fig. io)are on the second and the third 

 legs and are Hke those of C. affinis but less blunt. Those of the 

 third legs are the longer, sharper and more specialized in form. 



The stylet (Fig. 1 1) is short and simple, with the usual tuft of 

 setse absent from the median face which is very wide and flat. 



