INTRODUCTION. lui 



divisions are not invariable, nor are they separated by 

 any hard lines ; but such is the general condition of the 

 colony. In most of the tenantless zooecia a dark, more or 

 less spherical body occurs, which exhibits a definite and 

 uniform appearance. It consists of a mass of brownish 

 granular substance enclosed in a membranous cyst, the 

 inner walls of which are covered with reddish-brown spots. 

 It is generally placed about the middle of the zooecium, 

 occupying, in fact, the same position as the lower portion 

 of the digestive sac of the polypide, and, like it, is firmly 

 attached to the funiculus and to the network of filaments 

 Avhich proceeds from if^. This is the well-known ''brown 

 body " of authors (Woodcut, fig. xxi.) . Two or even more 

 may occasionally occur in the same cell. 



These bodies, which frequently give a dotted appear- 

 ance to the zoarium, are much too conspicuous to escape 

 the notice of observers ; and accordingly we find them 

 referred to by most writers on the Polyzoa from Ellis 

 downwards f. We are now in the region of controversy. 

 Around the " brown body " have gathered conflicting ob- 

 servations and rival theories. Its origin and its end have 

 been alike in dispute. Many of the opinions that have 

 been held about it no longer claim our consideration ; 

 they have already been finally disposed of. I shall here 

 confine myself chiefly to two opposite views of the nature of 



* See a paper by the author, entitled " Contributions to the History of 

 the Polyzoa," Quart. Journ. Micr. Sc. xiii. (n. s.), p. 24. 



t For a historical account of the various opinions entertained about them 

 see: — Smitt, "Bidrag till Eanuedomeu cm Hafs Bryozoernas Utveckling," 

 Ups. Univ. Arsskrift, 1863; the paper by the author, just cited, pp. 17-23 ; 

 and -Toliet, cyp. cit. pp. 7-9. They have been regarded as the remains of the 

 dead polypides, as ova, as ovaria, as statoblasts, as a secretion from the endo- 

 cyst, as a store of nutriment for the young polypide, as a reproductive body 

 formed out of the stomach of the decaying polypide. We may well say, 

 with Joliet, " Ces corps bruus out bien intrigue les observateurs " ! 



