288 WILLIAM A. HASWELL. 



spherical space. The secretions of these cells have two distinct 

 destinations. In the case of the more posterior cells of the 

 gland (PI. XXI, fig. 2, d.) the secretion passes out of the 

 cell by a narrow elongated neck or duck without well-defined 

 walls, and reaches the exterior by perforating the muscular 

 layers and passing through basement membrane, epidermis, 

 and cuticle by means of the delicate pore-canals. The 

 numerous " ducts " of these cells, which branch and anas- 

 tomose in their course, pour their secretion over a considerable 

 area of the ventral surface in front of and behind the genital 

 aperture, and all over the ventral surface of the sucker. The 

 function of these cells which discharge around the genital 

 opening is, doubtless, the secretion of the viscid matter by 

 means of which the eggs adhere together, while that of the 

 cells discharging on the sucker is the formation of a similar 

 sticky secretion adding to the adhesive power of the organ. 

 The most anteriorly placed of the cells discharge their contents 

 into a system of narrow anastomosing channels which run 

 between them. These channels unite on each side anteriorly 

 to form a larger duct which runs forwards into the region of 

 the head, past the excretory sac, and breaks up in front into 

 branches which open on the exterior (through the pore-canals) 

 on the ventral aspect of the tentacles. The secretion here 

 voided is a viscid matter similar to the secretion of the pos- 

 terior part of the gland, and its function is obviously to add to 

 the prehensile power of the tentacles. 



Scarcely to be distinguished from those subcutaneous uni- 

 cellular glands are certain gland-cells at the base of the penis, 

 secreting a substance containing spherical granules which 

 reaches the interior of the ejaculatory duct to become mingled 

 with the testicular secretion ; but, though apparently merely a 

 part of the subcutaneous system of unicellular glands, this 

 group of cells on account of the special destination of its 

 secretion is best considered along with the reproductive organs. 



The system of muscular fibres of the parenchyma 

 is highly developed. In general they occur either singly or in 

 narrow bands, running (PI. XXII, fig. 17, d.v.m.) either trans- 



