ALTERNATION OF GENERATIONS IN DOLCHINIA. 



483 



of the endostyle (es). From this diverticulum, the pericardial vesicle becomes 

 separated in late stages. It is probable that a part of the diverticulum is 

 retained here as an epicardium (p 368.). 



Of the form known as Dolchinia (KOROTNEFF, No. 82), the only colonies 

 which have been found have zooids corresponding to types II. and III. of 

 Ant-hinia (i.e., foster-forms and sexual gemmae, Fig. 251). The individuals 

 belonging to type II. (phorozooids) are here closely crowded on the common 

 colonial tube, while the sexual gemmae (g) develop on the peduncles of the 

 foster forms (in the same way, therefore, as in Doliolum). These foster forms 

 {phorozooids) of Dolchinia (z) become very easily detached from the colony 

 and then lead an independent pelagic existence. In the same way, the sexual 

 individuals sever themselves from the phorozooids. Migrating primitive buds 

 (u) may be seen on the colonial 



I A 



tube. These are able to move 

 from place to place (as was 

 stated by BARROIS for Doliolum 

 and Anchinia) by means of 

 large, amoeboid cells (c) adher- 

 ing externally to the bud on 

 each side (Fig. 252 A, a). Small 

 secondary portions (b) become 

 detached from the primary 

 primitive buds by fission, and 

 these either attach themselves 

 to the colonial tube itself and 

 grow into foster forms (phoro- 

 xooids), or else settle on the 

 peduncle of one of the develop- 

 ing foster forms and there 

 change into primitive buds of 

 the sexual gemmae carried by 

 that individual (Fig. 251, g). 

 The primitive bud seems to 

 produce only sexual gemmae, 

 and does not itself develop 

 further. For the further de- 

 velopment of the buds, which 

 has not been made out quite 



clearly, we must refer the reader to the statements of KOROTNEFF (No. 82). 

 Here also only an outer and inner layer of cells can at- first be dis- 

 tinguished. In the latter, a mass of large cells (Fig. 251 B, x) soon 

 separates from a mass of small cells. The large cells are said to be the 

 rudiment of the nervous system and the genital organs, while the mass com- 

 posed of small cells breaks up into three strands, the median strand (ph) 

 representing the rudiment of the pharynx, while the lateral strands are 

 thought to represent the muscle-rudiments. The atrium arises as an ecto- 

 dermal invagination, and the pericardial vesicle as a diverticulum of the 

 pharynx. 



771 



FIG. 252. A, Primitive bud () of Dolchinia 

 with two detached buds (b) ; B, Transverse 

 section through an attached bud of Dolchinia 

 (after KOROTNEFF). a, primitive bud ; b, 

 detached buds ; c, amoeboid transporting 

 cells ; ec, ectoderm ; m, muscle-rudiments ; 

 ph, pharyngeal rudiment ; st, epithelium of 

 the colonial tube ; x, mass of large cells. 



