828 " THETIS " SCIENTIFIC RESULTS. 



wall of the hydrotlieca by short strands affixed to minute 

 chitinous projections on the interior of the perisarc, a consider- 

 able distance above the apparent "base" of the hydrotheca. 

 The occasional occurrence of several series of the bright dots 

 which represent the projections, tells, as do repeated margins, of 

 successive generations of hydranths. 

 Gonosome. — Not represented. 

 Dimensions. — 



Hydrotheca, length of adnate portion... 0'49-0'56 mm. 



length of free portion 0-22-0-32 „ 



,, diameter at base 008-0 096 ,, 



,, diameter at mouth O'll-O 12 ,, 



Systematic Consideration. — Allman in his " Cliallenger "" 

 Memoir on the Hydroida (Pt. ii., p. 39) admits, as will anyone 

 who has paid attention to the genus, that there is "compara- 

 tively little to rely on " in distinguishing the species of Crypto- 

 laria. In such case, he has laid special stress upon the difFerences- 

 in the form of the ramification, but even this, he allows, "varies- 

 within very narrow limits." In the " Challenger " Report,, 

 almost all the species are primarily distinguished by their rami- 

 fication — a character liable to much variation induced by 

 environment. I am of opinion that, separated from minute 

 structural distinctness, diff'erences of habit cannot in general be 

 considered specific, and therefore I regard the present regularly 

 pinnate, flabelliform colonies, which in the main differ from 

 typical Cryptolaria covferta only in their habit, as belonging to 

 that species. But, indeed, Billard (1907, p. 178) has already 

 noted that, in specimens from the Bay of Biscay, from off Cape- 

 Spartel, Morocco and the Soudan, pinnate ramification prevailed.- 

 The minute structure and proportions of the hydrothecae of the 

 Australian specimens are similar to those described and figured 

 for Cryptolaria cov/erta, although the mouth diameter is a little 

 smaller than that of Allman's type specimens, judging by the 

 magnified figure of the latter given by Clarke in which the mouth 

 is represented as being 0'16 mm. broad. The remaining dimen- 

 sions agree with the type and with Billard's measurements. 



Pictet and Bedot (1900, p. 19), as also Hartlaub (1904, p. 13),. 

 and Browne^ ■^ express the opinion that CryjJtolaria crassicauliSf 

 Allman, 1888, is synonymous with Cryptolaria conferta, Allman^ 

 1877. After examination of portion of the type specimen of the 

 former, I must differ from those authors.^ ^ Apart altogether 

 from the habit of the colonies, an uncertain and untrustworthy- 

 character, sufficient s])ecific difference lies in the minute structure 



1* Browne — Journ. Mar. Biol. Assoc. Plymouth, viii., 1907, p. 29. 

 15 See Plate Ixxxvii. , fig. 4. 



