126 University of California Publications. IZoologt. 



relation to the potential alimentary canal of the ovicell polypide," 

 that is, to a bud which without the intervention of an ovum 

 would have developed in the ordinary fashion. And further, 

 "This potential alimentary canal grows round the ovum, losing 

 its previous form and becoming a compact multinucleated follicle 

 surrounding the egg ..." The study of a series of sections 

 from an ovicell-bearing colony, shows that the relations entered 

 into by the bud and ovum are of two sorts, each producing 

 opposite results. In the first the ovum develops, while the bud is 

 aborted. This includes all the cases of the first class {a) as 

 given above, and represents the only relation recognized by 

 previous observers. In the other, the polypide grows to maturity 

 while the ovum is aborted, and includes the second class (b) 

 above. To distinguish between the earliest stages of these two 

 possible relations is extremely difficult, if not impossible, since 

 before the cells of the bud heroine somewhat differentiated, there 

 is no criterion by which it can lie certainly known whether or not 

 an ovicell will result. Thus, in PI. XIII, Fig. 14, an ovum {ov.) 

 is showu in close proximity to a bud (p<l . 1x1. l) , but the out- 

 come of this relation cannot be predicted. Again in Fig. 15 

 several ova are seen in close connection with a group of small 

 cells (jid. bd. 2), but whether or not there is here an incipient 

 ovicell, cannot be asserted. Can the union indicated by the 

 proximal polypide hud of this figure (Fig. 15, p<l . bd. l) lie inter- 

 preted as the beginning of an ovicell'? This bud consists of a 

 long column of cells having a somewhat definite arrangement, 

 and caught at its proximal extremity is a large ovum. This, 

 for a time, was thought to represent an incipient ovicell, but the 

 conditions shown in Fig. 16 reveal its true meaning. But one 

 bud (p<l. bd.) is represented in this figure, and this has reached a 

 stage of development similar to that shown for the proximal hud 

 of the preceding figure (Fig. 15, pd. bd . l) . If we compare the 

 arraugement of the cells of the bud in these two cases, with buds 

 which represent early stages of undoubted polypide formation, 

 the resemblance is strong, and there can be no doubt that these 

 are stages in polypide development. Thus in PI. XII, Fig. 11, 

 are shown several instances of the earlier stages in the develop- 

 ment of a polypide. The cells in the upper portion of the bud 



