368 JV. S. xWICKERSON. [Vol. XVII. 



cilia in other places were colored only by orange, those of this 

 region took a decided haematoxylin color. It is possible that 

 the difference in staining qualities resulted from the presence 

 in that region of a secretion of cells such as I have described. 

 Oesophageal glands have not been described for other species 

 of Endoprocts. 



Mammary Organ. — I shall describe as a mammary organ a 

 peculiar modification of the epithelium of the floor of the atrium. 

 This organ is found only in females with embryos. The tissue 

 between the epistome and the opening of the oviduct becomes 

 swollen and rises up as a projection into the atrium (PI. XXXII, 

 Fig. 7; PI. XXXIII, Fig. 27), often extending as high as the 

 anus. The epithelium covering this elevation is very much 

 thickened, and the cytoplasm of the cells shows the presence of 

 granules which do not stain with iron-haematoxylin but are 

 faintly colored by orange. The nuclei of the cells are generally 

 near their basal ends, and the granules are most numerous in 

 the same region and fewer toward the free ends of the cells. This 

 condition is represented in PI. XXXII, Fig. 7, which is drawn 

 from a median sagittal section through an individual in which 

 the mammary organ is in a condition often observed both in 

 living animals and in series of section. 



A condition of the organ which has been observed in only 

 one case is shown in PI. XXXII, Fig. 5, which represents a 

 portion of a section deviating slightly from the median sagittal 

 plane. As there shown, the distal extremity of the mammary 

 organ has become secondarily invaginated, giving rise to an oval 

 sack-shaped cavity open at the end. This cavity is occupied 

 by a mass of nearly spherical cells filled with granules similar 

 in character to those already mentioned, but more completely 

 filling the cytoplasm. Many of the cells appear to lack a 

 nucleus, and where present it is small and inconspicuous. In 

 the atrium outside of the mouth of this sack are many loose 

 cells similar to those within the cavity. Although no con- 

 ditions intermediate between the two here figured have been 

 observed, it seems likely that the cells shown in the latter case 

 have arisen by a proliferation of the epidermal cells covering 

 the organ. The cells probably contain an elaborated food 



