xv, 6 Shaw: Campbellosphaera 501 



measures about 250 by 300 p. In June, 1919, it measured 230 

 by 285 ii. The somatic protoplasts are about 5 ^ in diameter 

 and the total cell width is about 10 fi. The estimated number 

 of somatic cells is 2,200. The general appearance of the somatic- 

 cells and their membranes resembles that of the asexual coenobia 

 at about the time when the gonidia divide. At the present time 

 the radial dimension of the somatic cells varies from about 20 p 

 between the oospores to about 10 ^ over the spores, grading 

 gradually from one size to the other. The protoplasts in all 

 the cells lie close to the convex or rounded outer end of the 

 somatic prisms. There are present twenty-three reproductive 

 cells which are scattered throughout the coenobium just under 

 the somatic layer except for a small vacant space about each 

 pole and another on each side of the coenobium. Applying the 

 simplest interpretation to them, I will call four dark ones, with 

 thin walls and diameters of about 37 /*, oogonia; and nineteen 

 paler ones, with thick walls and diameters of about 42 fi, oospores. 

 The protoplasm of both these kinds of cells is much denser than 

 that of the gonidia in any stage of the latter that has been 

 observed. Vacuoles are practically absent and the nucleus is 

 not evident. The thickened wall of the oospores fits loosely 

 and in optical section is wavy from reticulate wrinkles. The 

 spore wall seems to hinder the penetration of stains and other 

 reagents. An oogonium and two oospores from this coenobium 

 were photographed with a magnification of 400 diameters and 

 they are shown in Plate I, fig. 7. I have closely inspected this 

 specimen, and the six other specimens on the same slide, for 

 vacancies in the pattern of somatic cells and protoplasts which 

 might represent the sites, either of cells that became oogonia, 

 or of cells that had formed antheridia. I found only one vacancy. 

 It appears to be a somatic cell membrane of about one and a 

 half times the usual diameter, containing in place of a proto- 

 plast a cavity of about one and a half times the diameter of the 

 average protoplast. It lies beside (not directly over) one of the 

 oospores on the upper face of the coenobium. I am unable to 

 attach any particular significance to it. There is a number of 

 endophytic algae present in the somatic layer. The layer is 

 somewhat battered and broken, and one or more of the oospores 

 seem to have been fixed when about to make their escape. Each 

 of the neighboring coenobia in Plate I, fig. 6, contains seven 

 gonidia. 



A younger sexual coenobium (specimen 14) on the type slide 

 is shown in Plate I, fig. 8. It contains twenty-nine reproductive 



