Dr. A. Korotneff on Polyparium ambulans. 211 



fusiform cells, which pass off into processes ; the protoplasm 

 of the cells is rather coarsely granular. 



The entoderm of Pol2/pariumwsiS unfortunately insufficiently 

 investigated by me, and therefore I can hardly touch upon 

 such delicate questions as, for example, the nerve-cells or 

 nerve-fibrils. Almost throughout (figs. 4 and 9) the ento- 

 derm is one-layered, and consists of elongated cells which 

 show remains of flagella upon their surface. At the bottom 

 of the entodermal cells there are fine muscular fibrils, all of 

 which have a definite longitudinal direction, therefore parallel 

 to the long axis of the colony : these muscles never form 

 groups, but are distributed in a delicate layer. The re- 

 lation of the cell-bodies to the fibrils proves that we have 

 to do with entodermal muscle-cells. Between these cells 

 simple glands also occur (fig. 9, Dr). I may also mention 

 that the whole entoderm is filled with round, yellow, parasitic 

 cells {p^) ', these usually accumulate in such quantities that 

 the cell-nuclei are entirely concealed by them. These para- 

 sitic cells do not seem to occur in the gland-cells. 



With regard to the lower surface of the foot of Polyparium^ 

 it has already been mentioned that this is covered with small 

 acetabula (fig. 2) and that these acetabula are arranged in 

 rows and very accurately correspond with the buccal cones of 

 the upper surface. The structure of the whole ectodermal 

 layer, whether between or upon the acetabula, is quite uniform 

 throughout, differing only in thickness ; the thickest parts are 

 the margins of the acetabula, and then the middle, which is 

 separated from the margins by a groove. The histological 

 constitution of this ectoderm is quite different from that of the 

 lateral margin or the upper surface of Polyparium. When 

 taken from the middle of an acetabulum a section presents 

 the following peculiarities (fig, 6) : — Three layers are to be 

 distinguished in it; superficially there is a finely granular 

 glandular layer, in the middle a dense nuclear layer, and at 

 the bottom, lying directly upon the supporting lamella, a con- 

 siderable, finely fibrillar, fibrous layer. As in the ectoderm 

 of the wall-lamina, the whole ectoderm of the foot, from the 

 surface to the bottom, is traversed by the same elements. 

 Almost the whole mass consists of elongated gland-cells, at 

 the bottom of which (fig. 8, Dr) there is a cell-nucleus, 

 which marks off a fibrillar part extending to the supporting 

 lamella. These glands no doubt secrete the mucous substance 

 which accumulates in clots on the free upper surface. 



Among the glands many sense-cells occur, exactly like 

 those of the wall-lamina (fig. 6, sz). It seems to be a 

 remarkable fact that the sense-cells terminate directly upon 



