190 Mr. S. F. Harmer. Preliminary Note [Dec. 13, 



rise to an enormous number of spermatozoa. Fertilisation has not 

 been observed, although a testis may be developed by a polypide 

 which carries an egg, and although free, ripe spermatozoa have been 

 noticed in the immediate neighbourhood of young primary embryos. 



The primary embryo in its older stages is always in the immediate 

 neighbourhood of a "brown body," a structure which was found, 

 with rare exceptions, in the younger stages as well. Unless it should 

 hereafter appear that a " brown body " may be formed by the degene- 

 ration of a part of a polypide, the presence of this structure in a 

 zooecium containing an egg or a very young embryo clearly indicates 

 that the egg itself belongs to the second polypide which tenants the 

 zooecium. 



Every colony normally gives rise to an ovicell, although cases are 

 not uncommon in which degeneration sets in at an earlier or later 

 period, resulting in the atrophy of the embryonic tissues or in their 

 failure to develop further. 



Development of the colony and of the egg go on pari passu. The 

 details of the segmentation of the egg are even more difficult to observe 

 than in Crisia; but stages were found in which the number of embryonic 

 nuclei progressively increases. By the time that the embryo comes 

 to consist of four or five cells, it is surrounded by other cells which 

 form the commencement of a follicle. This structure is at first 

 composed of loosely-arranged cells, hardly distinguishable from the 

 " funicular tissue " which occurs in the body-cavity generally. The 

 follicle becomes more compact, and finally assumes a form which has 

 a striking similarity to a stage described by Kraepelin* in the early 

 development of Plumatella. In this condition the embryo consists of 

 a small spherical mass of protoplasm, including a few nuclei. It is 

 supported by a structure resembling the suspensor which supports 

 the embryo in flowering plants. This suspensor contains a very fine 

 lumen, and a section which passes longitudinally through its axis 

 accordingly shows two rows of nuclei, one row belonging to each of 

 the walls on opposite sides of the lumen. The suspensor and the 

 embryo are surrounded by a common investment of cells; and the 

 whole arrangement is attached either to the testis of the polypide or 

 to the lower end of the alimentary canal when no testis is present. 

 The embryo, with its investment, hangs down freely into the body- 

 cavity, and it is always in close connexion with the " brown body " 

 to which allusion has already been made. 



Kraepelin and Braemf are agreed in deriving the corresponding 

 structure in Phylactolaemata from a rudimentary polypide- bud, the 



* 'Abhandl. Naturwiss. Yer. Hamburg,' vol. 12, 1893 (Bryozoen), pi. 2, figs. 

 67, 68. 



t Leuckarfc and Chun's ' Bibliotheca Zoologica,' vol. 2, part 6, 1890 j see explana- 

 tion of fig. 171 (pi. 15). 



