907 



NATURAL SCIENCES OF PHILADBLPHIA, 



97 



containino; mucin, staining intensely 

 witli .Mayer's niucicarniinc; the na- 

 ture of the secretion of those of the 

 third type is undetermined. 



The glands of the first type (fig. 15) 

 are but few in number, and scattered 

 irregularly over the ventral surface 

 of the trunk. In form they are flask- 

 or sac-shaped, with a narrow and 

 constricted mouth. The mucus with 

 which they are filled appears nearly 

 homogeneous, although under a high 

 magnification it presents, in some 

 cases, a finely fibrillar structure. It 

 has, however, never been observed 

 to break up into blocks, as often 

 happens in mucous glands, as, for 

 example, in those of D. vorficoides, 

 as described by Schimkewitsch 

 (1S95). Flattened out against the 

 wall of the gland, and usually a little 

 to one side of its base, is found the 

 shrunken nucleus (n.), together with 

 the dark staining and scanty remnant 

 of the original cytoplasm. None of 

 the glands of this type were seen in 

 the act of discharging their contents. 



The glands of the second type (fig. 

 16) are also mucous glands, their 

 contents staining intensely in Dela- 

 field's hsematoxylin, in Conklin's 

 modification of this stain (1902) and 

 picrocarmine, as well as in IMeyer's 

 mucicarmine. They thus become very 

 conspicuous in examples mounted 

 entire, when stained in any of these 

 stains. Examination of individuals 

 thus mounted discloses the interest- 

 ing fact that these glands have, for 

 the most part, a fairly constant and sy 

 the exception of two groups on the 



Fig. III. — Diagrams illustrating the 

 distribution of the hj-podermal 

 mucous ghmds (second type), 

 from camera drawings of fixed 

 specimens. A, head, seen from 

 dorsal surface. 1-4, mucous 

 glands; c.gl., cephalic glands; 

 c.gl.d., duct of cephalic gland. 

 B, entire animal, seen in side view. 



mmetrical arrangement, and, with 

 last segment, vary but slightly in 



