314 J. H. ORTON. 



The most interesting record of the rate of growth obtained so far in 

 Actinians is that of Sagartia viduata, which has been found to attain to 

 full size at a maximum age of 14 to 15 months. 



EATE OF GROWTH IN SOME PORIFERA AND THE LIFE- 

 HISTORY OF SYCON, GRANTIA, AND LEUCOSOLENIA. 



Among Porifera a fairly complete investigation of the life-history 

 and rate of growth of Sycon coronatum, Grantia cofnpressa, and a species 

 of Leucosolenia has been made. These sponges have been found to be 

 annuals, as they have generally been believed to be. But the interesting 

 fact has been ascertained that there are two breeding seasons, especially 

 well marked in S. coronatum and Leucosolenia, one in summer and 

 one in late autumn. Data have, moreover, been obtained supporting 

 the view that the same specimens may breed twice in their life-history, 

 namely, once in late autumn and again in the following summer. Thus, 

 therefore, it would seem that temperature is the main factor governing 

 reproduction in these animals, since continuous rapid growth takes place 

 in the winter, as will be seen from the following observations. Some 

 very fine specimens of S. coronatum of known age have been obtained. 

 One exceptionally fine specimen attained a length of more than 28 cms. 

 with an average width of about 2-2 cms. in not more than 10 months 

 19 days, and growing during the period from July to May. Another 

 specimen 24-8 cms. long grew between June and January in a period 

 not longer than 7 months and 20 days. In another case several specimens 

 measuring between 14 and 16 cms. long grew between May and January 

 in a period not longer than 8 months and one day. It is an interesting 

 fact that none of these specimens yielded embryos when they were 

 isolated in dishes of sea-water, whereas tiny specimens from 3 to about 

 5 cms. taken in September and October gave off a good number of 

 embryos. These tiny specimens have been obtained from several 

 independent experiments started in early and late spring and in the 

 summer, hence they are the sponges derived from the embryos liberated 

 at the summer breeding period, namely, about the latter end of May or 

 early June. The approximate age of these specimens is therefore about 

 four months ; in one case the actual age of such specimens was not more 

 than 15 weeks. It is highly probable, moreover, that these autumn 

 breeding forms continue to grow through the winter and again give ofi 

 embryos in the following summer, when they die down. However this 

 may be, there can be no doubt that there are at least two broods of 



