48 DE. J. F. GEMMILL OK THE DEVELOPMENT OF 



ccelom, as well as from the lining of the hydrocoele, particularly in the neighbourhood 

 of pouches III and IV. Its general course is indicated by the line on PI. II. fig. 20. 

 Anteriorly it can be traced to a little in front of the groove which marks off the 

 preoral lobe from the body of the larva. At a slightly later stage one finds that the 

 fibrillse are short and somewhat matted, as might now be expected. One finds also 

 that they become connected anteriorly with fibrillae which, passing to the right side of 

 the body-wall and joining others coming from the region of the sucker, probably have 

 something to do with the production of the deep nuchal notch which is found in early 

 metamorphosis on the aboral side of the disc, and which afterwards in great part 

 becomes filled up to form the madreporic interradius (pp. 22, 27). 



Giliation. — In the adult the whole of the inner lining of the body-cavity, as well as 

 of the digestive sac and its appendages, carries cilia on its free surface. It was noted 

 on p. 13 that the primitive hypoblast of the gastrula is ciliated like the epiblast. In 

 the latter this condition is carried through and beyond metamorphosis. In the 

 former, however, it is difficult to trace continuity of ciliation, particularly in the case 

 of the middle chamber or enteron, but I believe that it occurs. 



IX. Mode of Obtaining and Eeaeing the Larv-^. 



The best way to secure material for the study of Solaster development is to keep 

 healthy adults through the spawning-season and to have the water circulation so 

 arranged that any ova that may be shed will not be swept away in the outflow. 

 As the eggs are lighter than water, this can readily be effected by drawing the 

 outflow from the bottom of the tank. In the end of March last (1910) three small 

 tanks at the Millport Marine Station were set apart for my use and fitted up in the 

 manner required. The outflow was effected by means of syphon-tubes, the inner ends 

 of which dipped down to the bottom, while, to prevent the possibility of excessive 

 emptying, the outer ends in each case dipped into a vessel the water-level in which 

 could not fall more than a few inches below that of the top of the tank. 



To begin with, all the available Solaster endeca were kept in the first of these 

 tanks. On March 30th one of the Starfish shed a large number of eggs, which 

 were duly fertilised in the manner previously described (pp. 9-10). All the Starfish 

 were then transferred to the second of the tanks, and on April 2nd the same female 

 again extruded a number of eggs which were fertilised in .their turn. The Starfish 

 were then put into the third tank, but no further shedding of ova took place. 



It is impossible, so far as I know, from the external characters, to tell with 

 certainty whether a specimen is male or female. Hence it is advisable to keep a 

 number together, in order to make sure that both sexes are represented. As happens 

 in other Echinoderms, a male is stimulated to emit sperm by the presence in the same 

 tank, even at some distance away, of a spawning female. Failing this effect, artificial 



