312 
BUIvI^ETlN OF THE BUREAU OF FISHERIES. 
least it is impossible to apply any theory of fixation which does not involve a fluid 
cement substance, engulfing both hairs and eggs, capable of setting under sea water 
and possibly in chemical relation to it into a firm ‘ ‘ hydraulic ’ ’ cement which is non- 
ductile under ordinary pressures when it is once set. 
I have spoken of the chorion as a tough membrane. That this is true is proved by 
the vicissitudes through which it passes unharmed. In egg laying the egg is compressed, 
being rod shaped in some forms when it passes the duct; it is therefore elastic, but it is 
only slightly ductile and then only when under great pressure. The freshly laid lobster 
eggs are spherical and as we have seen measure inch (1.5-1.7 mm.) in diameter; 
the egg embryo when ready to hatch is oblong, and measures about ^ inch (2.1 mm.) 
on the average of the sfiort and long diameters (fig. 33). This swelling in size, due to 
embryonic growth, stretches the chorion to great tenuity, until the limit of elasticity 
and ductility is reached, and the membrane bursts under the pressure, aided to some 
extent by the exertions of the larva. 
THE MALE SEXUAL ORGANS. 
The paired testes of the male are either distinct or united by a transverse bridge, 
and each give off a coiled duct or vas deferens, which opens by a valvular orifice on the 
inner side of the first segment of the last thoracic leg (fig. 2, pi. xliv). The duct con- 
sists of a proximal division which conducts the sperm from the testes, an enlarged glandu- 
lar part, and a terminal muscular or ejaculatory segment. A linear milk-white mass 
marks the course of the sperm through the transparent tube. In the coiled glandular 
division it is embedded in gelatinous envelopes or spermatophore-sacs {sph.) secreted by 
the lining epithelium. A sphincter muscle {sp. mu) produces an abrupt swelling at the 
beginning of the ductus ejaculatorius, the function of which is to eject the sperma- 
tophores. The latter have the appearance of semitransparent rods of vermicelli about 
an inch long, and consist only of opaque masses of sperm and the gelatinous medium 
described. When pressed out artificially, they imbibe water and swell perceptibly. 
SPERM CELLS, THEIR ORIGIN AND STRUCTURE. 
The sperm cells of the lobster (fig. 31) were apparently seen for the first time by 
Valentin in September, 1837, he gave a brief account of his discovery in the following 
year. A more aceurate account by Kolliker, who also remarked on the apparent immo- 
bility of the “rayed cells,” appeared in 1843, with figures, and notice of the “seminal 
sacs” or spermatophores. 
The structure and genesis of the spermatozoa of the lobster have been studied with 
much detail by Grobben, Gilson, Hermann, Sabatier, and more recently by Brandes (jj), 
Labbe (175) and Koltzoff (172). Probably few structures in the animal kingdom have 
been more puzzling than the rayed cells of the decapod Crustacea. The puzzle consisted 
in harmonizing the following conditions as generally found in these animals. The large 
eggs of crustaceans are surrounded by a tough chitinous membrane in which neither pore 
nor micropyle has been discovered. The sperm cells may be rounded or columnar, but 
