26 



HEMICHORDATA 



system and the anus. Each oviduct (ovcT) contains dark pigment, 

 which is seen through the dorsal skin on removing the tentacular 



arms. Eggs, each enclosed in a 

 stalked membrane, occur in num- 

 bers in the cavities of the gelatin- 

 ous house. The early stages of the 

 development are passed through 

 inside the tubes ; but there is at 

 present little other information 

 with regard to the embryonic de- 

 velopment of the Pterobranchia. 

 The specimen obtained by the 

 " Siboga " from Celebes is a male 

 colony with dimorphic individuals, 

 the reproductive organs being con- 

 fined to two-armed zooids with 

 vestigial alimentary canal. 



Eliabdopleura differs from 

 Cepludodiscus in its much smaller 

 size, 1 and it is perhaps due to 

 its minuteness that it does not 

 possess certain organs found in 

 the latter. The stalk is repre- 

 sented by a long muscular cord, 

 which is merely a narrow part 

 of the body. Basally the stalk 

 of each individual passes into a 

 common axis, which is for the 

 most part attached to the sub- 

 stance on which the colony is 

 FIG. 12. Small portion of colony of growing, and is to some extent 

 Rhabdopieura normani, Aiimau, branched. The muscular stalk 



Lofoten Islands, x 16. a, Anus ; . . 



p, proboscis (=buccal disc) ; r, rod- can be contracted into a spiral, 

 like axis of the adherent part ofthe thereb retracting the animal 



colony, prolonged into s, the stalks J 



of the individuals ; st, stomach ; t, into its tube. The stalks and 



tllG 7 OUn g er P artS f the axls 



which connects them are soft, but 

 the older parts secrete a dark brown cuticle, forming a narrow 



1 The diameter of a single individual removed from its tube is given by Fowler 

 as '123 mm. 



