NOTES AND OBSERVATIONS ON BOARD H.M.S. RATTLESNAKE 



diameter of the sphere there is a number of clear spaces — vacuolar — 

 varying in size from ^\r"d to -^-^jjoth of an inch, the smallest being 

 innermost. Scattered among the vacuolae of the innermost layer, 

 there were many of the yellow cells, and a multitude of very small 

 dark granules. Delicate, flattened, branching fibrils radiated from the 

 innermost layer, passing between the vacuolae, and in one specimen 

 these fibrils were thickly beset with excessively minute dark granules, 

 like elementary molecules, which were in active motion, as if circu- 

 lating along the fibrils, but without any definite direction. In this 

 case the whole body looked like a moss agate, so distinct were the 

 radiating fibrils (4 a). Left to itself for less than an hour, however, 

 this appearance as well as the circulation of granules vanished, and 

 only a few scattered radiating fibrils \\'ere to be observed, the rest 

 seeming to have broken off and become retracted. 



By rolling under the compressor the outer mass could be com- 

 pletely separated from the central dark body, which then appeared as 

 a spherical vesicle ^rVth of an inch in diameter (fig. 4 d), showing 

 obscurely a granular included substance. 



The membrane of the vesicle was very strong, resisting, and 

 elastic. When burst it wrinkled up into sharp folds (fig. 4 c), and 

 gave exit to its contents (fig. 4 d). These were — 



1. A very pale delicate vesicle (nucleus?) without any contents, 

 and measuring (but when much compressed) about ^Vth of an inch 

 (fig. 4 d). 



2. A heterogeneous mass consisting of (a) a finely granular base, 

 (i>) oil-globules of all sizes, (c) peculiar cells Ti-J-uth to ToVijth of an inch 

 in diameter (4 e). Some of these had a solid greenish red nucleus 

 about ^^^th of an inch in diameter. Others resembled the nuclei in 

 colour and appearance, but were larger (-jJuyth of an inch), and had 

 no cell-membrane : — were these granule cells ? 



Altogether the Thalassicolla nucleata might readily be imagined 

 to be a much enlarged condition of single cells of the Th. punctata ; 

 but I have no observations to show that it was so, nor can it be said 

 from which of the varieties of Th. punctata the Th. nucleata arises. 



The question may readily arise. Are these perfect forms ? I can 

 only say, as negative evidence, that I have never observed any trace 

 of their further development, and that the spicula and ' shells,' and 

 the capacity of fission, appear to afford positive grounds for believing 

 that they are not mere transitional stages of any more highly-organ- 

 ized animal. If, further, it can be shown that their structure is closely 

 allied to that of known organisms, this probability will, I think, 

 almost amount to a certainty. 



