98 PROCEEDINGS OF THE ACADEMY OF [Feb., 



number. Their usual arrangement is that illustrated in text 

 fig. Ill, A and B. As may l^e seen on examination of this 

 figure, the head bears seven of these glands, one median un- 

 paired gland near the anterior pole of the head (1), and three pairs 

 symmetrically grouped on its anterior surface (2, 3, and 4). On the 

 trunk their distribution is metameric as well as symmetrical, a row of 

 these glands encircling each of the trunk segments — except the first 

 and last — near its middle, just anterior to the ciliated bands. The 

 second segment commonly possesses five pairs of glands, the third 

 but three pairs, while the fourth and fifth segments have four pairs 

 each. On the sixth segment the glands of this type are divided into 

 two small groups, one occupying a crescentic area just above the anus, 

 on the postero-dorsal portion of the segment (fig. 18); the other group 

 lies on the ventral surface of the caudal appendage. 



All the glands of this, as well as those of the succeeding type, although 

 imicellular, greatly exceed in size any of the hypodermal supporting 

 cells; the gland, for example, represented in fig. 16 being 21 /i in length. 

 Owing to this circumstance only those glands which lie in the thicker 

 portions of the body wall, namely, those of the head and posterior 

 portion of the sixth segment, are permitted to assume a position per- 

 pendicular to the body wall. The others, which are situated in the 

 thinner portions of the latter, are compelled to lie in a plane parallel 

 to the surface of the body, their ducts being bent sharply near their 

 termination in order to reach the exterior. 



The individual glands are long pyriform in shape, generally some- 

 what bent, and often strikingly similar in outline to an old-fashioned 

 powder horn. At the base a crescentic theca of alveolar protoplasm 

 is present in every case, staining deeply in iron-hsematoxylin. Within 

 the protoplasm is contained a clear oval or crescentic nucleus (n.) 

 enclosing a large karyosome. The mucin which fills the gland is 

 always split up into distinct fibrils, longitudinally arranged, thus 

 giving the glands of this type a characteristic striated appearance. 

 Filling the mouth of the gland is a deeply stained plug of protoplasm. 

 None of the preparations studied showed a gland of this type in the 

 act of discharging its excretion. 



The glands of the third type (figs. 17 and 18, gl. 3) are much more 

 numerous than those of either of the preceding types. Their precise 

 manner of distribution, however, could not be determined with as 

 much certainty as that of the preceding type, owing to the fact that 

 they are not distinguishable on individuals mounted entire, but only 

 in sections. A study of the latter shows that on the head the glands 



