3 go MARGARET LEWIS NICKERSON. [Vol. XVII. 



classes — two glandular and one sensory and non-glandular. 

 The two glandular classes which he mentions are probably to be 

 identified with the glandular organs described in this paper, 

 although he makes no mention of intracellular sacks and ducts. 

 In regard to his third class, the sensory organs, I am not able 

 to infer such a correspondence, as he limits these organs to the 

 anterior and posterior extremities of the body, while in the pres- 

 ent account sensory organs have been described for the mid-body 

 region as well as the extremities of the worm. The histological 

 details of the epidermal organs, as given by Andrews, possess 

 but little in common with the observations here presented. 

 The sense cells of both types of glandular organs are not men- 

 tioned by him, and the large sensory organs with protruding bulb 

 seem also to have escaped his notice entirely, as he neither de- 

 scribes nor figures anything of the sort. His statement (p. 393) 

 that the delicate processes of the vacuolated gland cells of the 

 multicellular organs are to be regarded as nerve processes are 

 not supported by the observations here presented, and in view 

 of the modern conception of nerve fibers and their relationships, 

 such a condition as continuity of gland cell and nerve process 

 is highly improbable. The structure of the cells in the second 

 type of glandular organ has been very incompletely described 

 by Andrews ; the intracellular sacks and ducts and the relation 

 of these sacks to one another being unnoted, as well as the 

 extreme variety of conditions presented by these structures. 



Ward ('91), in his paper on the anatomy and histology of 

 Sipunculus nudus, describes a condition of the bicellular 

 glands of this Gephyrean which resembles to a slight extent 

 the condition found in the second type of glandular organs 

 described in this paper. He says (p. 153) : "Whether resting 

 or active, a clear zone of plasma forms the periphery of the cell 

 on all sides, and is, therefore, adjacent to the vacuole as well as 

 to the external surface of the cell. This zone is traversed radi- 

 ally by delicate fibrils, the beginnings of the plasma reticulum 

 which fills the cell, but which is ordinarily seen only in this clear 

 zone." These delicate fibrils are probably to be compared with 

 the filaments surrounding the intracellular sack in the gland 

 cell, as figured in this paper. Ward states that the gland cells 



