Report on the Hydroids. 349 



hydrothecae, which I have identified as belonging to the following 

 species: Lafoëa friiticosa, Cahjcella sijringa, Ciispidella procumbens and 

 Stegopoma fastigiatiim; the last-mentioned species was only taken at 

 this station. 



St. 104^b. 200—250 m. Clay and gravel. A small stone with 

 Lafoëa friiticosa. 



Bathymétrie distribution of the species 



comp. Tables 2 — 5. 



According to the information given by the Journal as to the 

 nature of the bottom, the algal vegetation seems to cease down towards 

 100 meters. For this reason I have thought it most correct, in the 

 tables of the bathymétrie occurrence of the species, to place St. 95 a 

 where the depth is stated to be ca. 50 — 100 meters and which con- 

 tains some Delesseria, in the column 60 — 100 meters; and St. 64a, 

 where the depth is giл'en as ca. 100 m. and which is without vege- 

 tation, in the column 100 — 200 m. The material from St. X, for which 

 the depth and bottom are unknown, is not included in the tables. 



In these tables I have used statements of frequency, as other- 

 wise a wrong impression is obtained of the bathymétrie distribution 

 of several species. We may note, for example, that Lafoëa friiticosa, 

 Ciispidella procumbens and Cahjcella sijringa are certainly found 

 from 6 m. down to more than 200 m., but the great majority of the 

 specimens are found in dephts about 20 — 40 m. 



I use the ordinary signs of frequency: rr = very rare, r = rare, 

 -|- = neither rare nor common, с ^ common, cc = very common. 



One may perhaps object to these tables, that the material for 

 many species is too small to permit of any conclusions being drawn. 

 This objection is, of course, correct in the case of the really seldom 

 species, but it must be remembered, that the statements of frequency 

 are relative; they are proportionate to the whole material, which is 

 very large. It is quite probable that the species which occur in 

 greatest abundance, are to be found at more stations and at more 

 different depths than the less abundant species; but about the oc- 

 currence of the latter certain valid conclusions can be drawn. Thus 

 it may be said, that Halecium labrosiim and Coryne eximia possibly 

 occur in smaller or greater depths than those mentioned, but that 

 they are certainly in the main found in 20 — 60 m.; and the most 

 important thing is, to find out under what conditions a species 

 thrives best, though it is of course also of interest to know in how 

 small or how great a depth it can be found. On this last point 

 the tables only give reliable information for the commoner species. 



