THE AMERICAN LOBSTER. 
159 
letter S, passes to the back of the last thoracic leg. The sperm may be traced along 
the course of the tube as a central, milk-white, linear mass of closely packed sper- 
matozoa. In the glandular segment this is surrounded by a transparent, jelly like 
substance which is secreted by the glandular epithelial cells (spermatoplioral glands) 
lining this part of the duct. This is gradually constricted into the terminal (c) muscu- 
lar segment , or ductus ejaculatorius , which ends in a valvular opening. A sphincter or 
swelling of the muscular layer is seen at the beginning of the ductus ejaculatorius, 
serving to force out the sperm. 
The two distal segments {b, c) were called the penis or “verge” by Milne Edwards 
and Brocchi, because it was supposed that they were evaginated in copulation. It 
has been already pointed out that the evagination of these parts is mechanically 
impossible, a sufficient reason for dismissing this supposition. 
The structure of the different sections of the vas deferens is illustrated by plate 
37. The planes of section are marked in fig. 120, 1 to 5. As Grobben has already 
shown (83), the vas deferens is surrounded by a distinct membrane and is composed 
of a connective tissue wall, inclosing muscles, and a lining epithelium; the latter gives 
rise to secretions which mingle with the sperm aud surround it with protective envel- 
opes. The connective tissue is fenestrated, abounds in blood channels, and the 
muscular tissue is disposed into an inner stratum of longitudinal fibers and an outer 
layer of circular bundles. 
At the extreme proximal end of the duct (fig. 124) the epithelium is apparently 
stratified and the wall is thin. The tube is filled with a solid mass of ripe sperm (sp) 
and a surrounding coagulable fluid, which is the direct secretion of the epithelial cells. 
As the glandular segment is approached the epithelium becomes distinctively col- 
umnar (fig. 125). The glandular segment (figs. 127, 128) is partly subdivided by the 
infolding of the epithelium (/). The spermatophores (in some cases there are two) are 
restricted to one chamber and are immediately surrounded by a yellowish secretion 
(Spr.), which is probably formed in the proximal segment and stains very feebly in 
carmine. The remainder of the spacious cavity (a and b) is filled with a less dense 
coagulable substance which stains freely in carmine. Bodies resembling yolk-spheres 
can sometimes be seen. 
Grobben says that the secretion of the glandular segment of the vas deferens 
of the crayfish appears chalky-white in reflected light and consists of small, shining 
granules. 
In the ductus ejaculatorius (fig. 126) the muscular coats are strongly developed and 
the epithelium appears to secrete an albuminous, granular substance. The height of 
the columnar or cylindrical cells varies very much, as Grobben remarks, according as 
they are squeezed more or less closely together. 
The external opening of the vas deferens is formed by an invagination of the skin, 
and according to Grobben is paved with thick cuticle. 
SPERMATOPHORES. 
The sperm is ejected from the muscular segment of the vas deferens in the form 
of spermatophores, which consist of elongated packets of sperm cells, surrounded by 
gelatinous capsules, the origin of which we have just seen. The spermatophores can 
be pressed out of the ducts when these are removed from the body. They quickly 
imbibe water and swell perceptibly when wet with it. The spermatophore is composed 
of two distinct secretions, as was first pointed out by Grobben. According to the 
