1880.] THE GENUS GTRASIA. 297 



of tlie sLoiter portion (Plate XXVI. fig. 3, a) to the aperture within 

 the vagina and ovo-testis (Plate XXVI. fig. A,j. sp.). 



Macrochlamys decussata, of which I have a drawing, taken when 

 the animals were in coitu, protruded a large white bladder-like sac, 

 winch expanded and contracted from time to time as if inflated with 

 air ; tills I now think may have been the spermatheca drawn out and 

 receiving tbe penis and capreolus. 



In the two specimens I examined, the spermatheca (sp.) was 

 elongate, smooth, lying close to and partly enveloped by the con- 

 volutions of the oviduct &c., with its posterior end near tbe junction 

 of the hermaphrodite duct and albumen-gland. This posterior 

 termination is bent over on itself, presenting a smooth rounded end 

 (Plate XXV. figs. 2 & 4), which, coiling round, terminated, and was 

 covered with what was apparently muscular tissue buried in the 

 prostate find oviduct. The form of the spermatheca is due to its 

 contents ; and the ronnded end is produced by tbe bending-over of 

 the flagellum-like terminations of the enclosed spermatophores. 



In oae specimen of G. hookeri which I examined, probably taken 

 in the cold weather, all tbe generative organs are small and con- 

 tracted, the spermatheca only represented by an attenuate sac. 



The amatorial organ or dart-sac (D)' is a long cylindrical body 

 narrowing towards the genital aperture, and again swelling there 

 into a large orifice j it has a very thick and muscular structure, and 

 in these spirit-specimens is very hard and unyielding. When cut 

 open longitudinally, the dart or spicuhnn amoris was found to be a 

 simple cylindrical rod, sharply pointed (Plate XXVI. fig. 7). This 

 organ has a strong retractor muscle, with its attachment near that of 

 the penis. 



Relative Position of the different Parts in G. gigas. — On cutting 

 through the skin of the upper side of the back, commencing from 

 between the eye-tentacles, the penis is seen lying in the middle line 

 between the inverted eye-tentacles (Plate XXV. fig. 2) ; on the proper 

 left of it are seen three large convolutions of the inlestine (i); and on 

 laying it over to the right side the salivary glands of flattened form 

 are seen spreading over these, and a distinct connexion with the 

 central convolution was very clearly made out (fig. .5, a). Pro- 

 ceeding from the sides of the buccal mass will be noticed two strong 

 muscles, which have their attachment on the frontal margin of the 

 body-cavity, at the point (Plate XXIV. fig. 3) m ; these are the re- 

 tractor muscles of the head and buccal mass. 



The spermatheca lies on the right side of the animal, covered 

 partly by the oviduct ; and a large expansion of the intestine occupies 

 the posterior portion of the cavity, narrowing suddenly to enter that 

 of the shell above. 



A very large mucous gland lies next the sole of the foot along the 

 whole length of the body-cavity ; and two large pedal nerves are con- 

 spicuous and traverse it, throwing off nerves to the epidermis, and 

 extend onto the caudal gland. 



1 Glandula mucosa cum sagittA amatoria. 



