REPORT ON THE HEXACTINELLIDA. 438 



In regard to the number of species found at the different localities this general fact 

 may be noted, that at most of the stations only one or two species were found, while 

 only a few yielded several or many forms. The statistics on which I based this result 

 in my preliminary communication' have been slightly altered by the additions of some 

 localities, and by changes in the determination of a few species, but these modifications 

 are on the whole unessential, and the results stand thus. Of the fifty-eight soundings on 

 the occasion of which Hexactinellida were found — 



34 yielded only 1 species. 



In his work La vie au fond des Mers, Filhol cites the statistics in question from my 

 preliminary notice, and adds the following remark : — " II resulte de ce tableau que dans 

 plus de la moitie des cas les especes d'Hexactinellides ont ete trouvees isolees. Cette 

 observation ne concorde pas avec celles que nous avons pu faire dans la parti e de 

 I'Atlantique nord, parcourue avec le Talisman, oil les chaluts n'ont rapporte qu' 

 exceptionellement une seule espece. Les Askonema ont et6 trouvees avec les Aphro- 

 callistes ; les Hyalonema, les Euplectelles etaient preque toujours associees." A possible 

 solution of this apparent divergence in the results of two deep-sea expeditions, will be 

 alluded to below when the general results as to the geographical distribution of the 

 Hexactinellida are summed up. 



The number of individuals of the same species found at one place is but rarely 

 considerable. Generally only one or two specimens of each species were obtained at the 

 same locality. Sometimes, however, a considerable number of specimens were found at 

 once, as was the case with Farrea occa near St. Thomas, West Indies, Aphrocallistes 

 hocagei ofi" Bermudas, Rossella antarctica near the Kerguelen Islands, Polylaphus 

 2)hilippinensis and Pheronema glohosum at Little Ki Island, Hyalonema depression in 

 the middle of the North Pacific, and finally, Crateromorplia meyeri, Polylophus 

 philippinensis, and especially Euplectella aspergillum at the Philippine Island, Zebu. 

 Of the latter indeed, which was eagerly sought after, in a well-known locality, nearly a 

 hundred specimens were obtained. 



As to the richness of the difi'erent seas and regions in Hexactinellida, it is, in the first 

 place, of interest to notice the absolute number of species found in the three great oceans. 

 The following tables (IV. and V.) exhibit the state of the case in regard to this and 

 similar points : — 



1 Narr. Chall. Exp., vol. i. part i. p. 449. 

 (ZOOL. CHALL. EXP. — PART LIIL — 1887.) Ggg 55 



