86 BULLETIN OF THE 



the phytoid stocks of Bugula, and in creeping corms like Lepralia or 

 Cristatella, may be explained as affording additional strength on the one 

 hand, and as a device for saving space on the other. 



The absence of true dichotomy, which I have sought to show charac- 

 terizes the budding of Bryozoa, is interesting as seeming to indicate 

 the fundamental similarity of the process of budding in Paludicella to 

 that found elsewhere. The tip of the branch does not divide equally 

 in the first nor in the other instances, but constantly maintains its 

 precedence, giving off parts of itself to form lateral branches. These 

 parts may grow out at right angles to the primary branch, as in Palu- 

 dicella, but generally they gi'ow forward nearly parallel to it, as in 

 most marine Gymnolsemata. 



In Bugula (Plate VII. Fig. 64°') branches are always given off 

 toiuard the axils, and therefore an ancestral branch gives off all lateral 

 branches from one side and the successive orders of branches are given 

 off alternately to the right and left. In Crisia, on the contrary, branches 

 are given off ahaxially, and they ai'e given off not from one side only, 

 but alternately to the right and left. In both cases the two facts are 

 mutually dependent. The fi.rst case gives rise to a stock in which the 

 branching tends as greatly as possible towards compactness and the for- 

 mation of a closely built stock ; the second case gives rise to a diffuse 

 and loosely built stock (cf. Figs. 64, 65, and 64% 65*) . In the sec- 

 ond case there is a maximum space to each individual ; in the first, 

 a maximum economy of space. 



The rule that lateral buds on two closely related branches tend to 

 arise in the same generation is one that, as has been shown, is more 

 or less apparent in some cases, but is easily obscured by other rules. 

 May not the tendency be due to the same causes that produce the 

 synchronism of division in related cells of a cleaving egg 1 



That lateral buds should occur in Bugula flahellata on the outermost 

 rows only is not surprising when we reflect that there is abundant room 

 on the margin, whereas the inner individuals are hemmed in from lat- 

 eral expansion by the pressure of adjacent rows. This is very mai'ked in 

 certain repent colonies, as, for instance, occasionally in Membranipora 

 (Plate VIII. Fig. 70). Here the intermediate branches 6, 7, 8, and 9 

 have produced no lateral buds for many generations, while almost every 

 individual of the marginal rows has given rise to a lateral branch. It is 

 merely a result of the same cause, it seems to me, that lateral budding 

 occurs more frequently in Bugula turrita at the margins of fans than 

 elsewhere. Here there is room to spread. 



