434 Mr. T. H. Huxley on the genus Thalassicolla. 



nous masses of very various form ; — elliptically-elongated, hour- 

 glass-shaped, contracted in several places, or spherical, varying 

 in size from an inch in length downwards ; showing no evidence 

 of contractility nor any power of locomotion, but floating pas- 

 sively on the surface of the water. 



Now of such bodies as these there were two very distinct 

 kinds : the one kind, consisting of all the oval or constricted, and 

 many spherical masses, is distinguished to the naked eye by pos- 

 sessing many darker dots scattered about in its substance ; the 

 smaller kind, always spherical, has no dots, but presents a very 

 dark blackish centre, the periphery being more or less clear. I 

 will adopt the provisional name of Th. punctata for the former 

 kind, and that of Th. nucleata for the latter, as a mere matter of 

 convenience, and without prejudging the question as to the ex- 

 istence of specific distinctions. 



Th. punctata. (PL XVI. figs. 1, 2, 3.) 



The mass consists of a thick gelatinous crust containing a 

 large cavity. The crust is structureless, but towards its inner 

 surface minute spherical, spheroidal or oval bodies are imbedded, 

 from which the appearance of dots arises. These are held to- 

 gether merely by the gelatinous substance, and have no other 

 connexion with one another. Each " spheroid " is a cell, with a 

 thin but dense membrane, ^ jnfik to - 2 j^ th of an inch in diameter, 

 and contains a clear, fatty-looking nucleus T ^ n th to ^J^th of an 

 inch in diameter, surrounded by a mass of granules which some- 

 times appeared cellseform. 



This fundamental structure — a mass of cells united by jelly — 

 like an animal Palmella, was subject to many and important 

 varieties. 



Very commonly the central part of each mass, instead of con- 

 taining a single large cavity, consisted of an aggregation of clear, 

 large, closely- appressed spaces, like the " vacuolar " of Dujardin 

 (figs. 2, 3, 2 a, 3 a). 



Very frequently also each cell was surrounded by a zone of 

 peculiar crystals somewhat like the stellate spicula of sponge, 

 consisting of a short cylinder, from each end of which three or 

 four conical spicula radiated, each of these again bearing small 

 lateral processes (figs. 3 «, 2 b). 



In another kind, much more rarely met with, the spherical 

 cell contained a few prismatic crystals about T oV(T tn °f an mcn 

 in length ; it was of a bluish colour, and enveloped in a layer of 

 densely packed minute granules not more than yj^o o^ n °^ an 

 inch in diameter. Outside these there was a number of spherical 

 bright yellow cells T -^ ^ th of an inch in diameter, and inclosing the 

 whole a clear, transparent brittle shell perforated by numerous 



