472 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Cambarus a solution has been given above for C. afjinis. In Astacus 
further observations are needed to determine these two points; but 
according to Whitman (’91, p. 401) it was suggested by Leuckart 
that the walls of the sperm tubes gradually harden and compress the 
contents till, in Astacus, they flow out at both ends; and the same 
authority credits Meyer (’77) with the idea that not water but the 
secretion that fastens the eggs to the legs causes the spermatophores 
to discharge, in certain decapods. The latter suggestion with the 
added assumption that the ends of the spermatophores may close 
up and hold the sperm sealed from the water till the time of laying 
when the mucus of the abdominal cement glands might act, seems a 
good working hypothesis in the case of Astacus. 
Whatever may prove to be the method of preservation and discharge 
of sperms in Astacus, the habit of placing spermatophores over con¬ 
siderable areas of the female, is, obviously, less specialized and less 
perfect than the employment of the annulus as a sperm receptacle, 
in Cambarus. And since comparative anatomy is held to indicate 
that Cambarus is a higher development than Astacus we may suppose 
the annulus, as a sperm receptacle, to be a recent acquisition. 
In this connection it is of interest to note that in Cambarus a smaller 
amount of sperm would seem necessary since in the annulus it stands 
at a point of vantage to meet all the eggs while in the diffuse distribu¬ 
tion in Astacus much might be wasted. This is in harmony with 
actual measurements of the vasa deferentia of an Astacus leniusculus 
and of a Cambarus afjinis. In the former, lengths of 220 and 230 mm., 
in the latter 60 mm. only, indicated a probable ability of the Astacus 
to provide more sperm. 
The conclusion here reached by comparative study of adults, 
that the trumpet of the annulus is a recently acquired epidermal 
pocket, has recently been supported by a study of its ontogeny 
(Andrews,: 06 ) for it was there shown that the sperm pocket arises 
as a mere epidermal groove, which gradually secretes thick exo¬ 
skeleton and becomes complexly folded. 
The employment of a sperm receptacle made as a chitinous pocket 
on a somite differing from that discharging the eggs is a perfection in 
indirect sperm transfer met with again only in the lobster. As Bumpus 
(’91) showed, there is in Homarusamericanus a chitinous sperm pocket 
having a similar position to, and presumably the same mode of use as, 
the annulus of Cambarus. But it does not seem that this sperm recep- 
