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 rejiresent tliose parts of tlie zooecial wall which, later, form the 

 stai'ting point of the lateral buds. 



It Avas pointed out by ISTitsche (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 Avell as by their method of 

 budding. For example, ISTitsche found that the primary zooecium in 

 Flustra memhranacea is remarkably similar to that of Merabranipora, 

 and with respect to budding agrees with Memhranipora j^i^osa as 

 described by Schneider (N'o. 5), i.e., a number of buds here appear, 

 whereas the secondary zooecia of Flustra memhranacea, 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, Avhile the buds produced from it grew into zooecia 

 of normal shape. 



Heteromorphous development of single individuals often occurs in 

 the Ectoprocta. Thiis in the polymorphous stock there may be 

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

 organs known as ooecia, oviceUs, avicularia, and vihracula which are 

 regarded as polypides modified in adaptation to a special function. 



B. The development of Statoblasts. 



A special kind of asexual midtiplication is Ijrought about in the 

 Phylactolaemata by the production of peculiar reproductive bodies, 

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

 back to budding. The recent researches of Krabpelin 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 statoljlasts 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 Avith a ring of air-cells which serve 

 as a float (sr). In the germ-body Ave 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 Ave regard the superficial epithelium as the ectoderm 

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



e 



