ANDREWS: ANNULUS VENTRALIS. 
471 
and filling the basket-like space formed when the female then placed 
herself upon her back and bent her abdomen forward over her ster¬ 
num. 
Immediately after laying and for two days longer, sperms in the 
expanded form were seen in the mucus near the eggs. These sperms 
had apparently escaped from the spennatophores, which were merely 
tubes of material secreted by the walls of the vasa deferentia and filled 
with sperms. The emptied walls of the spermatophores remained 
attached to the abdomen as small, white, leathery threads of tenacious 
mucus as late as eight to ten days after the eggs were laid. 
There is here no pocket to receive the sperm and though some spe¬ 
cies of Astaeus have a simple enlargement of the sternal plate of the 
fourth thoracic somite, included by Hagen in his conception of the 
annulus, yet this is a solid mass and not a pocket. 
Comparing the modes of indirect sperm transfer in Cambarus and 
Astaeus we see that in both the vasa deferentia secrete tubes about 
the sperm mass and that the sexual habits of the male and female 
in both species are closely similar. But in Astaeus the secreted 
tubes full of sperm are deposited over considerable areas of the ven¬ 
tral side of the female, in pieces which we may call spermatophores. 
There they remain till the eggs are laid when they somehow discharge 
the sperm into the secreted mucus that envelops the eggs. And in 
Cambarus the secreted tubes full of sperm do not form spermatophores 
or short persistent lengths, but the sperm in them is passed directly 
into the exoskeletal pocket of the annulus and sealed in there, by 
some of the material of the wall of the secreted tube, probably. All 
the sperm given to the female here remains inside the pocket of the 
annulus till the eggs are laid, when it escapes into the mucus in 
which the eggs are enveloped. 
Chantran describes the sperm of Astaeus when near the eggs as 
like those in the spermatophores and in the vas deferens and all in 
the expanded form. In Cambarus, however, the sperms are still 
in the coiled up form when they leave the annulus, and facts else¬ 
where given (Andrews, : 04a) make it probable that in Astaeus also 
the sperms really remain coiled up till near the eggs. 
Probably the sperms in Astaeus require protection from water as 
they do in Cambarus. How they are protected and how they are 
liberated at the right time to meet the eggs, are difficult questions to 
be solved concerning many arthropods that have spermatophores. In 
