HYDROZOA — RITCHIE. 



82D 



of the hydrotheca. Examination of tlie following table indicates 

 a marked difference in size and proportions : — 



Hydrotheca, length of 



adnate portion.. 

 Hydrotheca, length of 



free portion 



Hydrotheca, diameter 



at base 



Hydrotheca, diameter 



at mouth 



Cryptolaria conferta. 





0-6 

 0-3 

 0-1 

 016 



— . CD 



0-35-0-50 



0-26-0-385 



y 



0-14-0-16 



9. 5 

 n SI. 

 P-i m 



•49-0 -56 

 0-22-0 -32 

 0-OSO096 

 0-11-0-12 



Cryptolaria 



CRASrilCAULIS. 



rH en S 



1-0 

 70 

 0-08 

 0-26 



< ^ 



0-92-0 -98 

 0-52-0 -83 



o-os-ou 



0-29-0-35 



Measurements are in millimetres. 



These differences aie visible, firstly in the very much larger 

 size of the hydrothecse of Cryptolaria crassicaulis, and, secondly, 

 in the shape of the hydrotheca ; for while those of C. crassicuidis 

 are four times as wide at the mouth as at the base, those of C. 

 conferta are only one and a half times. The greater narrowing 

 emphasises the tapering of the liydrothecte in V. crassicarilis and 

 produces a cornucopia appearance, distinct from the almost 

 cylindrical shape of the hydrothecse of C. conferta. In the speci- 

 mens before me there is also a gi-eat difference in the robustness 

 of the perisarc, which is more strongly developed in C conferta, 

 (the smaller in dimensions) than in C. crassicaulis, as I he follow- 

 ing measurements indicate. But differences in thickness of jjeri- 

 sarc are frequently of no significance specifically. 



C. conferta. O. crassicaulis. 



Thickness of outer wall of hydrotheca 12-22/i ... 9-15;u 

 Thickness of adnate wall of hydrotheca 



at buse 14-27/i ... 11-15/^ 



Thickness of general perisarc 15-24/x ... 9-19/x 



I am of opinion, judging from the size and shape of the hydro- 

 thecse, that the specimens doubtfully recorded by Hartlaub from 



16 These measurements, estimated from magnified figures, must be taken 

 as approximate only. 



*'' See Plate Ixxxvii., fig. 4. 



