xv, 6 Shaw: Ca?npbellospfiacro 503 



Specimen IS. — 270 by 340 m. Somatic plastids, about 5.3 v. Somatic 

 cells, about 11.9 m; number, about 2,660. Oogonia, none. Oospores, 17; 

 outer wall, 44 m; protoplast, 37 n, eccentric. 



A sexual coenobium (specimen 19) containing- both oogonia and 

 antheridia is shown on Plate I, fig. 9, a micrograph taken June 

 18, 1919, from another slide (No. 4) of the same lot as the type 

 slide (No. 2). It measures about 180 by 195 p. The diameter 

 of the somatic protoplasts is about 5 p, and of the cells including 

 the membranes 7.1 p. The estimate of the number of somatic 

 cells is 2,460. There are present in the coenobium 25 oogonia 

 and 3 antheridia, together with two masses of matter which 

 may represent disseminating antheridia. The oogonia are about 

 24 /i in diameter. The antheridia are platelets 33, 34, and 36 

 p, wide, and about 6 p thick. They are more or less convex on 

 what I take to be the ciliated side. All three present edge views. 

 One is on the right side near the anterior pole, one on the right 

 side near the equator, and one on the left side midway between 

 the equator and the posterior pole. The count of cells in the 

 median optical section of a platelet is about 14, which number 

 corresponds aproximately to the diameter of a platelet containing 

 128 spermatozoids. The distribution of the reproductive organs 

 in the coenobium is as follows: 



Anterior quarter 1 oogonium. 1 antheridium. 



Second quarter 11 oogonia. antheridium. 



Third quarter 7 oogonia. 2 antheridia. 



Posterior quarter 6 oogonia. antheridium. 



Total 25 oogonia. 3 antheridia plus 2 ? 



Two other sexual coenobia on the same slide have the following 

 characters : 



Specimen 20.— 215 by 220 ^. Somatic protoplasts. 5 m; cells, 8.5 m; 

 number, 2,360. Oogonia, 29; about 28.5 m; absent in anterior quarter, and 

 leaving open spaces on the near and far sides of the coenobium. 



Specimen 21. — 200 by 210 p.. Somatic cells, about 7.1 m; number, about 

 2,960. Oogonia, 11; 25 »; oospores, 8; 30 m; smaller reproductive cells, 

 3; 14 to 18 ,u; remains of sperm masses (?), 3. Reproductive cells absent 

 from the anterior third of the coenobium. 



An asexual mother coenobium (specimen 22) containing both 

 asexual and sexual daughters is shown on Plate II, fig. 10, a 

 micrograph taken on June 18, 1919, from a third slide (No. 6) 

 of the same lot. Specimens such as this serve to establish the 

 fact that asexual and sexual coenobia, such as have been de- 

 scribed in the foregoing paragraphs, occur in the same species. 

 This evidence is not superfluous, for on the slides of this lot 



