BUDDING. 49 



and its capacity for regenerating, and at this point the polypide-rudiment arises 

 (p). Two islands of germinating tissue which persist at the two sides of this 

 rudiment represent those parts of the zooecial wall which, later, form the 

 starting point of the lateral buds. 



It was pointed out by Nitsche (No. 23), and more recently by 

 Pergens (No. 27), that the oldest individuals of the Bryozoan 

 colony, and above all the primary zooecium derived from the larva, 

 may, in many cases, be distinguished from the other normal zooecia 

 of the colony by their shape and size as well as by their method of 

 budding. For example, !N"itsche found that the primary zooecium in 

 Flmtra membranacea is remarkably similar to that of Membranipora, 

 and with respect to budding agrees with Membranipora pilosa as 

 described by Schneider (No. 5), i.e., a number of buds here appear, 

 whereas the secondary zooecia of Flustra membranacea, as a rule, 

 produce only one bud each at the distal end. Pergens also found 

 that the primary zooecium of Microporella passed through a Mem- 

 braniporan stage, while the buds produced from it grew into zooecia 

 of normal shape. 



Heteromorphous development of single individuals often occurs in 

 the Ectoprocta. Thus in the polymorphous stock there may be 

 found, besides the usual individuals, root-processes, and specialised 

 organs known as ooecia, ovicells, avicularia, and vibracula which are 

 regarded as polypides modified in adaptation to a special function. 



B. The development of Statoblasts. 



A special kind of asexual multiplication is brought about in the 

 Phylactolaemata by the production of peculiar reproductive bodies, 

 the so-called statoblasts. This form of development may be traced 

 back to budding. The recent researches of Kraepelin and Braem 

 prove that the statoblasts are undoubtedly encysted persistent buds, 

 intended to secure the continuance and distribution of the fresh- 

 water Bryozoa during the winter months. 



The lenticular statoblasts or winter eggs (Fig. 27 B) consist of a 

 mass of cells, the germ-body, enclosed in a thick cuticular envelope 

 (c), the latter is usually provided with a ring of air-cells which serve 

 as a float (sr). In the germ-body we can distinguish a superficial 

 epithelium, discovered by Reinhard (Fig. 27 A, ec), and a granular 

 cellular mass rich in yolk (d). The structure of the germ-body can 

 therefore be compared to that of the Ectoproctous embryo described 

 above (p. 15), if we regard the superficial epithelium as the ectoderm 

 and the granular inner mass as the equivalent of the central tissue. 



E 



