OF THE KERGUELEN REGION OF THE GREAT SOUTHERN OCEAN. 417 



HOLOTHURIOIDEA 1 : 



Chirodota contorta' 1 Ludwisj. 

 *Cucumaria kerguelensis, Theel. 



Kerguelen specimens as a different species [Hemiaster cordatm~\. Dr Studer and Mr Smith enumerate it as a distinct 

 species in their lists of Kerguelen Echinoderms. . . . From the evidence furnished by the large material collected by 

 the Challenger, there seems but little doubt that species which have thus far been distinguished as Hemiaster australis, 

 philippii, and cavernosus are all different stages of growth of one and the same species, but owing to the great difference 

 in structure between the ambulacral petals of the males and females, and the extraordinary changes this species passes 

 through from its youngest stage until it has reached its adult sexual form, it was very natural that these several stages 

 of growth should od scanty material have been regarded as so many distinct species. The coloration of specimens from 

 different localities appears also quite distinct, and in some cases the test and spines are of a light brownish-yellow, in 

 striking contrast to the dark coloured specimens found at other localities.- — (Agassiz, Zool. Chall. Exp., part 9, pp. 

 183-4.) 



1 The examination of the vast harvest brought home by the Challenger Expedition from different regions of the 

 world, from the shore as well as from the abysses of the ocean, shows clearly that those Holothnrids which live in the 

 deep sea have two different derivations. The great majority are Elasipoda, which cannot be derived from the present 

 shallow-water fauna, but must have originated from a past type that certainly bore another stamp. On the other 

 hand, so far as can be judged from the results of the expeditions hitherto made, the remaining Holothurids met with in 

 the great depths are comparatively few, both in species and individuals, and unmistakably show the closest relation to 

 the present shallow-water fauna ; so that while the Elasipoda have retired toward the abysses an infinitely long time 

 ago, the latter have emigrated only at a comparatively much later period. . . . With regard to the bathymetrica 

 distribution of Apoda and Pedata, our present knowledge does not enable us to speak of any results of very general 

 value. However, the Challenger Expedition has been successful even in these respects, several important discoveries 

 having been made, proving that the present shallow-water fauna has far more outposts in the great depths of the 

 ocean than at first supposed. Before the Challenger Expedition set out, only a very few forms belonging to the Apoda 

 and Pedata were known from depths exceeding 100 fathoms, and scarcely one below 200 fathoms. This list [of the 

 species met with in the deep sea at depths from 500 fathoms and under] induces me to believe the following remarks 

 to be true, or, at least, to have some probability : 



1. Descendants of the recent shallow-water Holothurioidea have escaped to the greatest depths at which any 

 living Holothurid has been obtained, viz., 2900 fathoms, but they are by no means so prevalent as the Elasipoda, nor 

 do they form such a characteristic feature in the abyssal fauna. 



2. Most of the forms met with in the deep sea below 500 fathoms are distinct from the shallow-water species 

 though they belong to the same genera. 



3. Several species have a vast bathymetrical distribution, some individuals of them still living near the shore, others 

 having descended without any obvious change in their organisation into the considerable depth of 500 to 700 fathoms 

 or exceptionally even deeper. 



4. A wider distribution seawards of a species seems to take place preferably in the northern and southern oceans, 

 where the different belts proceeding from the vicinity of land outwards would seem to have in general a greater 

 uniformity in temperature and other physical conditions than in the tropical and subtropical regions, where it is 

 stated that the belts below 100 or 200 fathoms have lost the influence of the climate, etc., and present conditions of life 

 far different from those above them. Such forms are Myrotrochus rinkii from shore to 500 fathoms ; Echinociwumis 

 typica from about 40 to 530 fathoms ; Thyone raphanus from 20 to 672 fathoms ; Holothuria intestinalis from 10 to 650 

 fathoms ; Holothuria tremula from 20 to 672 fathoms ; Trochostoma violacea from 20 to 700 fathoms ; Thyonidium 

 pdltiddum from about 30 to 1081 fathoms, etc. The two deep-sea species of Synapta are scarcely distinguishable from 

 some of the shallow-water species. 



5. Pcelopatides, Pseudosticlwpus, Acanthotrochus and probably even Aakyroderma are the only true deep-sea genera 

 of Apoda and Pedata, no representatives of them having hitherto been obtained near the shore or, at least, from any trifling 

 depth. Species of these genera very seldom seem to thrive at a less depth than 500 fathoms. 



6. Among the Apoda the Synaptidae are, with a very few exceptions, shore forms, living near the surface of the sea, 

 while the Molpadidje are probably in a state of emigration seawards, a great number of them having already reached 

 the abysses and settled there. 



7. The Dendrochirotae and Aspidochirotse are still true shore or shallow-water forms, though there are even here 

 many exceptions, proving that their representatives are thriving even at great depths. — (Theel, Zool. Chall. Exp., part 

 39, pp. l, 2, 6, 7.) 



2 It is remarkable that the forms [of Chirodota purpurea] dredged at the Falkland Islands are devoid of any 

 sigmoid deposits, while those found by the Challenger Expedition in the Strait of Magellan and at Kerguelen 



