52 BULLETIN OF THE 



in successive generations beyond the seventh increases more and more 

 slowly, and finally decreases to zero. Thus the average rate of increase 

 of individuals in the generations 7 to 10 over those in the preceding is 

 only 16%. 



One finds here, as elsewhere, that the number of individuals cut by 

 any unit of arc, the primary individual being taken as a centre, remains 

 practically constant, whatever the radius of the arc. 



In studying the creeping stocks of Cheilostomes (Plate VIII. Fig. 71), 

 young corms have been chosen because they exhibit fewer irregularities 

 of formation than old ones. Such irregularities are chiefly due to some 

 imevenness of the surface on which the corms lie, but sometimes 

 apparently to a crowding of individuals. Old rows of individuals are 

 occasionally entirely cut off and end in the middle of the stock ; some- 

 times two rows running side by side, perhaps derived from a common 

 ancestor, suddenly merge into one again. In one case, Escharella varia- 

 bilis, Verrill, I have seen three rows thus merge into one at the margin, 

 suggesting the existence of a samhwpp (common bud) in the sense of 

 Smitt ('65, pp. 5-16). Ostroumoff {'^Q% pp. 338, 339) has observed 

 a case in Lepralia Pallasiana. He says : " Dans quelques cas, qu'on 

 peut consid6rer comme des anomalies, il arrive parfois que deux bour- 

 geons, provenant de loges differentes, viennent a se fusionner." It seems 

 to me, therefore, that while Nitsche ('71, pp. 445, 446), who opposed 

 with such vehemence and success the idea of Smitt that zooecia arise from 

 an undivided marginal zone of cells, was quite right in affirming ('71, 

 p. 447) that even the smallest marginal zooecia are sharply marked off 

 from the adjacent ones, yet he overlooked the possibility that under 

 certain circumstances the lateral walls might fail to develop, and thus 

 one zooeciura might arise in the place of two, or even three. 



I have not read Smitt's Swedish paper, but I do not find anything 

 in the translation given by Nitsche to warrant the latter's conclusion 

 ('71, p. 446) that Smitt believed the " Gesaramtknospe " to be " formed 

 from the sum total of the mature peripheral zooecia." If I understand 

 Smitt, ho conceived the samhiopp not to be derived from the most 

 peripheral mature zooecia, but to be self-proliferating, and to give rise 

 to the rows of zooecia, not to arise from the\n. It is the " bud of 

 the colony," not the sum of the buds of the peripheral individuals of the 

 stock. In this I would agree with him exactly. Although usually one 

 finds the marginal gemmiparous tissue forming the lateral walls at the 

 extreme edge of the corm, and thus apparently separated into wholly 

 distinct adjacent gemmiparous masses ; under certain conditions, the 



