122 BULLETIN OF THE 



instead of one. Reichert ('69, p. 311, Fig. 28, Plate VI.) has shown 

 that in Zoobotryon (one of the Ctenostomata) "an der Mantelflache, 

 und zwar einseitig, inseriren die Bryozoenkbpfe mit Alternation in par- 

 allelen, wie es schemt, langgezogenen spiralig verlaufenden Reihen an- 

 geordnet." Nitsche (75, p. 370) states that the buds in Loxosoma 

 arise from the mother alternately on opposite sides, and that the 

 younger the bud, the nearer it is to the foot of the parent individual. 



Both Hatscheck (77, pp. 517, 518, Fig. 33, Plate XXIX.) and Seeli- 

 ger ('89, p. 176) show that in Pedicellina young individuals are devel- 

 oped in the plane of the older ones, and are successively formed at the 

 growing tip of the stolon, towards which the oesophageal side of all 

 individuals is turned. This relation is the same as that which we have 

 found in Cristatella. In Cheilostomata, however, it is apparently the 

 anus which is turned towards the budding margin. 



Thus, throughout the group of Bryozoa, we find that the position which 

 young buds assume in relation to older individuals is very definite. 



I am inclined to believe that the radial partitions of Cristatella sep- 

 arate the morphological equivalents of the isolated branches of such a 

 form as Plumatella punctata (see Kraepelin, '87, Taf. V. Figs. 124, 125). 

 The type of budding which gives rise to the series of median buds may, 



then, be represented, as seen from the side, by 

 Figure B. The margin (*) will then represent 

 that portion of the body-wall of the youngest 



individual, which will give rise to a part of 

 Figure B. . 



the body-wall of the next younger individual. 



The process by which the body-wall of the individual of Cristatella is 

 formed is therefore, in my opinion, different from that which Braem 

 describes in the case of Alcyonella, for he maintains that in Alcyonella 

 the proper body- wall of an individual arises later than its polypide. In 

 fact, the tip of the branch of Alcyonella is somewhat different from 

 that of Cristatella. In the former, it is occupied by the polypide of a 

 budding individual ; in the latter, a part of the body- wall of the bud- 

 ding individual is pushed out beyond the polypide. In the former, the 

 foundations of the daughter polypide are pushed out upon the body- 

 wall of the mother, and begin to form their own proper body- wall; in 

 the latter, the young bud migrates away into the modified part of the 

 body-wall of the mother, which forms the extremity of the branch, and 

 which now becomes a part of the body-wall of the daughter polypide. 

 This distal part of the body-wall grows independently of the polypide 

 by interstitial growth, and thus differs from any part of the body-wall 



