508 E. A. MINCHIN. 



found. It will be noticed that the three lower (inner) cells 

 are more deeply stained than the three upper (outer) ones. In 

 fact, the three lower nuclei are as deeply coloured as the 

 nucleus of the neighbouring spicule-cell^ while the three upper 

 nuclei are scarcely at all deeper than the nuclei of the flat 

 epithelium. 



The above facts are strong evidence for believing that it is 

 the inner formative cells which are concerned with the first 



SEXT. 



Fig. a. — Very young triradiate system in its sextet. X 1600. fl. ep. Flat 



epithelium, sext. Sextet. 



appearance of the spicule rays, but the point cannot be con- 

 sidered as established with certainty. 



A very important point with reference to the young spicule 

 is the fact that its three rays appear to be at first quite 

 separate from one another. In some cases the distinctness of 

 the rays is extremely obvious, especially in the very young 

 spicules of CI. coutorta (PI. 41, fig. 48) ; in other cases it is 

 not so obvious, and fusion of the rays seems to take place very 

 early (PI. 40, figs. 31, 32). The smallest spicule seen by me 

 was in a preparation of CI. coriacea, and the three rays were 

 like three bacteria, about 1^ ju in length; they appeared to be 

 in contact at their inner ends, but the minuteness of the 

 spicule and the thickness of the cells rendered it impossible to 

 make out their exact relations (see woodcut. Fig. A). As the 

 rays increase in size their separation from one another becomes 

 more marked, and is generally quite distinct in spicules with 



