241 



Figure 



chilensis 



189; Caudina 



(Inaba, 1930). 



Pentactula before settling. Preoral lobe 



has disappeared. Primary tentacles 



protrude from the oral cavity. Ciliated 



bands are still retained. 



larvae is quite close to direct development. In 

 Cucumaria frondosa (Edwards, 1909), for ex- 

 ample, the pentactula hatches from the enve- 

 lope with five tentacles and one ambulacral 

 podium. 



A review of the literature shows that 

 development with lecithotrophic larvae is of- 

 ten found in species of the order 

 Dendrochirotido (see Table 7). Moreover, in 

 this order as well as in Apodida, either brood 

 care or direct development is characteristic of 

 many species. At present, nearly 30 such spe- 

 cies are known, among which almost half are 

 inhabitants of polar and adjacent regions. 

 Such, for example, are the Dendrochirotida 

 species Cucumaria laevigata and Psolus 

 koehleri and the Apoda species Taeniogyrus 

 controtus from the Antarctica, and the Dendrochirotida species Cucumaria 

 glacialis from the Arctic. Brood sacs also occur in one Sakhalin species, 

 namely, Thyone imbricata (order Dendrochirota). 



Brood care of the young in cold-water sea cucumbers takes place in 

 various brood sacs or pockets, which are specific dermal processes. In several 

 species (Psolus antarcticus, Psolus granulosus, Psolus punctatus, Psolus figulus, 

 Psolidium incubans, Cucumaria parva, and Cucumaria curata) the young are 

 carried on the smooth part of the creeping side (Hyman, 1955). 



It is interesting to note that in tropical sea cucumbers the young develop 

 inside the body coelom of the mother. Sometimes lecithotrophic larvae de- 

 velop in such sea cucumbers. In Apodida the larva of Chiridota rotifera 

 (Clark, 1910) retains the ciliary cover while Synapta vivipara (Clark, 1898, 

 1910) does not, even though the larva of this sea cucumber develops through 

 the same stages as does Chiridota rotifera. One more type of brood care has 

 also been identified, wherein development of the young takes place in the 

 ovaries of the female. This type of development has been described in par- 

 ticular for the Antarctic Apodid, Taeniogyrus contortus (Hyman, 1955). 



Besides brood care, instances of direct development are known in sea 

 cucumbers. In this case the eggs are spawned in water and the juvenile 

 develops avoiding both the auricularia and doliolaria stages. Development in 

 Thyone briareus (Ohshima, 1925) and Holothuria floridana (Edwards, 1909) 

 proceeds in this manner. 



The feature common to species with brood care and species with direct 

 development is the presence of large yolky eggs. A list of species of sea 

 cucumbers and their type of development is given in Table 7. 



