222 Shaw: Merrillosphaera africana 197 



MALE COENOBIA 



Coenobia that contain, besides the somatic cells, only large 

 numbers of androgonidia that divide to form bundles or plate- 

 lets of sperms were first described by Ehrenberg under the name 

 Sphaerosira volvox. Since it has been recognized that these 

 are the male coenobia of species of Volvox they have been known 

 as the Sphaerosira stage of the species in which they occur. 



That male coenobia of the Sphaerosira type occur in Merrillo- 

 sphaera africana is demonstrated by specimen 7, in which asex- 

 ual, bisexual, and male progeny occur in the same mother 

 coenobium. Since the two species of Merrillosphaera occur 

 mixed in most of the collections, description of the unborn males 

 in their distinguishable mothers is more important than de- 

 scription of the free males concerning the identity of which there 

 may be question. The only male coenobium in this little series 

 of photomicrographs of typically ovoid coenobia at Manila will 

 now be described. , UM-tfcl 



Specimen 7ft.— Plate 2, fig. 7. The unborn male coenobium in 

 specimen 7 is of the same size and shape as its twin sister. It 

 measures 265 by 383 „ in its flattened condition. The average 

 spacing of the cells is between 21 and 25 ,, Taking it as 22.5, 

 and the mean diameter of the coenobium as 302* the number 

 of cells indicated would be 6,500. The size of the somatic pro- 

 toplasts ranges from about 4.5 „ at the back to about 7 , at the 

 front. The protoplasts of the twin sister coenobium are of the 

 same size. Those of the smaller sister are all about 4 * Those 

 of the mother coenobium range about from 6 to 1 * The area 

 in the front that contains no androgonidia is small. The an- 

 drogonidia are about from 12 to 15 , wide and all undivided 

 It is estimated that in a given area they are about five times as 

 numerous as the oogonidia of the twin sister. T" 1 ^ 

 number of about one hundred fifteen. They are ottered rather 

 irregularly under the coenobium wall. Some are in pairs that 

 are in contact, some in rows of three, and some form chains of 

 cells that are not far apart. 



The free male coenobium shown in Plate 2 fig. 8, is not from 

 the same source as the material described. It will be considered 

 with its associates as specimen 24. 



FORMS WITH SOMETIMES MORE THAN FOUR GONIDIA 

 A FORM WITH SOMETIMES SIX GONIDIA 



From the same pond, I, that supplied the material that in- 

 cluded the specimens already described, there was obtained two 



