ALEXANDROMENIA AGASSIZI. 139 



The component gland cells are arranged into numerous lol)ules, which gener- 

 ally extend from the surface of the gland tu tlie main central duct. These 

 are separated from each other by delicate connective-tissue sheaths, which fre- 

 quently contain small blood sinuses, and are traversed by a slender canal which 

 apparently does not function as a duct. The evidence is not altogether 

 conclusive but from a careful study of sections it appears that the secretion does 

 not pass through the cavity of the lobule, but is contained in delicate ductules 

 which arise in the gland cells. Arri\ing at the central cavity of the gonoduct 

 the darkly staining secretion makes its escape through the lining epith(>liuni by 

 means of intercellular openings. 



The epithelium of the main duct is composed of high colunniar cells which 

 contain a finely granular lightly staining glandular substance. About the termi- 

 nal section of the coelomoduct, where the eiMthelium become lower and the 

 secretion scant in amount, a heavy sheath of circular muscles appears and con- 

 tinues to the cloacal cavity. 



As might be expected in an animal of tlie size of this species the circulatory 

 system is well developed and of more than ordinary complexity owing to the large 

 number of sinuses which hold po^sitions in and aroimd the various systems. 

 The heart, having the usual position, consists of two distinct divisions (Plate 7, 

 fig. 5), an auricle and ventricle. The walls of both of these are of uncommon 

 thickness, but otherwise present no especially noteworthy features. They are 

 connected by a tubular stalk which projects slightly into the cavity of the ven- 

 tricle and may serve as a valve. 



From the front end of the ventricle blood passes through numerous openings 

 in the somatic musculature to unite into one tube, the aorta, which from the out- 

 set appears to lack any trace of an endothelial lining. As it coui'ses forward 

 dorsal to the reproductive gland it originates numerous vessels which ramify 

 through the body wall or passing ventrally between the halves of the gonad 

 forms a subgenital sinus. In the head region it expands considerably and 

 communicates with extensive lacunae in and between the body wall and the 

 alimentary canal. The blood in these spaces makes its way to the ventral 

 surface where it unites into one main canal, immediately ventral to the gut, 

 which connects also with several small channels coursing along the folds in the 

 ventral furrow. At the posterior end of the Ixjdy this ventral sinus courses 

 dorsally, keeping close to the under surface of the gut, and when opposite the 

 junction of the auricle and ventricle it divides into two short branches which 

 pass backward on each side of the rectum. These last named vessels are very 



