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BISCAYAN PLANKTON. 



Part VI.— THE COLLOID RADIOLARIA. 



JBy E.. NoRRis WoLFENDEN, J/.D., F.L.S., F.Z.S. 



Eead 1st June, 1905. 



The collection handed to me for examination by Dr. G. H. Fowler vvtis contained in 

 80 bottles. Of tliese, in a few instances, the material was in a condition difficult of 

 identification. While such species as Thalassicolla and Choenicosplicera (in which the 

 sliell presents sufficiently distinctive characters) are comparatively easy of determination, 

 it must be borne in mind that the determination of species of CoUozoum except in the 

 very recent or actually living condition is always a matter of considerable difficulty, 

 often of impossi'bility, and the diagnosis of such species is here presented with the 

 neces'-ary reserve. 



The material to hand contained few species, but an overwhelming preponderance of 

 one of them, viz. Chcenicosphcera, which appeared in no less than 67 gatherings. 



CoLLOZOUM INEKME, Haeclicl. 



Very few intact " sausage-shaped " colonies were found. In most cases the colonies 

 were oval or more or less round and in young condition. One long colony was 1.5 mm. 

 in length, 1 ram. broad. All trace of segmentation was lost. The closely-packed 

 individuals contained each one central oil-globule, and were of 'O^S diameter sur- 

 rounded by niimerous green cells round the zooids. This was the only intact long 

 colony, evidently in the young condition. 



In all cases the diagnosis must be regarded as doubtful in the absence of the 

 occurrence of re2:ular seo'mented and vacuolated colonies and the determination of the 

 behaviour under osmic acid, chromic acid, &c. 



CoLLOZOTJM Brandti, Wolfcndcn. 



A few instances occurred of- rounded colonies about 4 mm. diameter, containing zooids 

 of 1 mm. diameter, each with one central oil-globule and 25-30 xanthellae. The colonies 

 showed no trace of vacuolation. One such colony of about 30 mm. diameter contained 

 700 zooids. In one instance a few diatoms, long and spindle-shaped, were found lying 

 between the zooids, of characters identical with those which I have described as occurring 

 in the CoUozoum of the Pairoe Channel, to which I gave the name C. Brandti *. The 

 diagnosis of this species is again given under reserve, but it is undoubtedly nol 

 C. inerme. 



Spn-EROzouM: punctatum ?, Miiller. 



In only one sample occurred a small colony of this species (not iu very good 

 condition). 



* Journal Miuiiie Biological Association, vol. vi. p. 344 (1902). 

 SECOND SERIES — ZOOLOGiT, VOL. X. 23 



