136 SIDNEY F. FARMER. 



ovicell is still in the main cylindrical (or really pyramidal), 

 and does not yet differ materially from an ordinary zooecium. 



Stage E. — Development of the Cavity of the Embryophore and 

 Enlargement of the Ovicell. 



The general external features of the ovicell in this stage 

 are seen from figs. 31 and 32, both taken from one colony. 

 The embryophore of fig. 31 is shown in back view in fig. 30, 

 and is a rather late representative of stage D, as can be seen 

 by comparison with fig. 16, the nutritive tissue being clearly 

 indicated on the proximal side of the brown body. The 

 combination of an embryophore in stage D with an ovicell in 

 stage E has already been seen in fig. 24<. The embryophore 

 of fig. 32 is in stage E. 



The cavity of the ovicell is beginning to expand distally in 

 figs. 31 and 32; in preparation for the great increase in the 

 size of the embryophore which is to take place during the 

 succeeding stage. The distal end of the embryophore in both 

 ovicells lies at the level marked Emb., and it is thus interest- 

 ing to note that the embryophore is still in the part of the 

 ovicell which represents its zooecium-stage. 



The growing margin of the ovicell has already acquired 

 the characters of stage E, consisting of a deeply staining mass 

 of tissue which extends round the growing edge of the ovicell. 



Fig. 32 shows that the growing edge is uniformly curved in 

 the upper wall of the ovicell, while below it has an undulating 

 course, due to the fact that the floor of the ovicell is ridged 

 by the upgrowth of the young zooecia in the way that has 

 already been described (p. 79). 



I believe that the position of the growing edge shown in 

 figs. 31 and 32 is not completely normal, but that the action 

 of reagents has caused it to shrink away from the edge of the 

 calcareous parts. This seems to be indicated by fig. 31, in 

 which the protoplasmic growing edge practically coincides with 

 the distal margin of the roof of the ovicell on the left of the 

 figure, though it has shrunk away from it to the right. 

 Sections show that the stained line seen in the figures is 



