ECHINODERMATA 



413 



of tlie narrow neck is to be considered as such. The entero- 

 coeles in Antedon separate from the common fundament of 

 the intestine and hydrocoele at a very early period. 



In the development of Antedon the statements of Goette, Barrois, and 

 Bury are opposed to one another. In what precedes we have followed 

 those of Barrois, for they agree fairly well with those of Bury. Differ- 

 ences between these two authors exist in so far as, according to Bury, the 

 two processes from the neck, connecting anterior and posterior vesicles, 

 unite and together constitute the intestine, which at first is circular in 

 form, and through which there extends for a while a solid cord, uniting 

 the two enterocoeles. Furthermore, according to Bury, only the larger 

 portion of the anterior vesicle represents the fundament of the hydro- 

 coele; the smaller portion, after separating from the hydrocoele, still 

 supplies a part of the body cavity (anterior body cavity), and later is 

 connected with the outer world by means of a canal, whereas a union 

 of this part of the body cavity with the hydrocoele and the formation of 

 the stone canal take place only secondarily. According to this, a part 

 at least of the enterocoele would arise at the same time as the hydro- 

 coele. According to the statements of Barrois, on the other hand, the 

 hydrocoele in this case, contrary to all other Echinoderms, takes its origin 

 independently of the enterocoele. The same is to be gathered from 

 Goette's description, which, however, it is difficult to harmonize with 

 those of Barrois and Bury. 



Features appear in the development of Antedon which, 

 besides influencing the shape of the archenteron, also modify 

 its derivatives, the enterocoele and hydrocoele. In accord- 

 ance with the attached mode of life of the later larval 

 stages, the farther development also exhibits important 

 deviations from the development of the other Echinoderms. 



Statements on the Development of the Entero-hydrocoele not 

 in accord with the Preceding.— The studies of N. C. Apostolides on 

 the development of two Ophiurans {Ophiotrix versicolor [Lusitanica Lin., 

 cf. Fewkes, No. 13] and Amphiura squarnata) also contain statements 

 on the mode of formation of the water-vascular system, but the results 

 are so different from anything hitherto known of Echinoderm develop- 

 ment that we mention them only on account of their remarkableness. 

 In both forms the gastrula is said to arise not by invagination, as is 

 known to be the case in other Echinoderms, but rather by delamination. 

 Likewise the fundament of the loater-vascular system is said to be de- 

 veloped in a different way, namely, by an accumulation of two masses of 

 cells, one on either side of the archenteron. These, according to the 



