240 E. A. ANDREWS 
earthworms, spiders, some cephalopods and leeches. The es- 
sence of these cases of indirect sperm transfer lies in the fact that 
while the sperm is transferred by organs, and not by floating, 
yet these organs either do not put the sperm into the egg passages, 
or else if they do they are not organs directly concerned with the 
discharge of sperm, or both may be true. In indirect sperm trans- 
fer there is no true copulation, or intromission, but at most con- 
jugation or clasping. 
The three methods are not always sharply separable, and may 
be regarded as only convenient groupings of physiological processes 
that occur here Andgthere among animals without reference to 
their systematic positions. The diffuse method is obviously the 
one open to the most hazard in the sperm and eggs meeting; the 
direct method by intromission the best assured method; the in- 
direct method most perculiar and needing special explanation in 
each case. 
In the crayfishes and lobsters most interesting cases of indirect 
sperm transfer occur, and it is the purpose of the present paper to 
describe the organs of the males that are used to transfer the sperm > 
to the receiving organs that have been described in previous com- 
munications (1, 2, 3). In these animals the male transfers the 
sperm to the outside surface of the female where it remains till 
the eggs are laid, when fertilization takes place outside the body. 
In the American lobster and the sixty and more species of cray- 
fishes of the genus Cambarus that are found in all but the most 
western parts of North America, the sperm on the shell of the 
female is stored in a special pocket, or receptacle, but in the other 
genera of crayfishes, all the world over, there is no such receptacle . 
and the sperm is believed to be distributed over the shell of the 
female in separate spermatophores. While the sperm pocket has 
been described (1, 2, 3) the organs of the male that fill the pocket 
have had only such consideration as was necessary for the sys- 
tematist, who found them to be of the greatest value in distin- 
guishing species and in forming subgenera. 
In the present paper the anatomy of the male organs is exam- 
ined and their use as organs of sperm-transfer is explained. 
