ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 21 



Coelenterata give off medusas when not more than a month old. The 

 commonest species of Tubularia — almost certainly Tubularia larynx — 

 was found to give off actinulae larvae at an age of six weeks, and in one 

 experiment this form had moderately developed gonophores in 26 days. 

 As these actinulre have been found to settle and grow into polyps within 

 a few days, it follows that this species may pass through its life-cycle 

 within six weeks, and probably under favourable conditions within four or 

 five. Plumularia and Clonothyra3a may complete their life-cycle in three 

 months, and in both cases probably in a period shorter than that by 

 some weeks if the conditions are favourable. Most of the Ccelenterate 

 species investigated appeared to have a maximum rate of growth in the 

 months of August and September. Sagartia viduata was found to attain 

 full size at a maximum age of sixteen months. Among Porifera, Sycon 

 coronatum and Grantia compressa were specially investigated. They 

 were found to be annuals, as has been generally believed. There are 

 two breeding-seasons, summer and late autumn, and there was evidence 

 that the same individuals may breed twice — once in late autumn and 

 again in the following summer, after which they die down. Growth 

 continues throughout the winter, and temperature appears to be the 

 main factor in reproduction. Among Polyzoa, Bugula flabellata was 

 found to grow to a good sized colony and give off larvge within eight 

 weeks. A raft moored at sea for six weeks was found to be covered 

 with a growth of the hydroid Obeha genicidata, on which adult Nudi- 

 branchs, chiefly Galvina picta, were feeding. Masses of spawn of G. picta 

 were found on the hydroids, and from these masses free-swimming 

 veligers were given off. Thus, these ISTudibranchs had undoubtedly 

 peopled the raft as veligers, rushed through their development at 

 the expense of the hydroids, and were giving off veligers again to 

 populate hydroids elsewhere within a period of not less than six weeks 

 and two days. Many other interesting examples of rate of growth and 

 age of reproduction are given, but fuller accounts and more precise 

 figures are reserved for a later paper. Meantime the investigator asks 

 his readers for references to work on the same subject which they may 

 know of. 



Tunicata. 



Colouring Matters of Diazona violacea.* — Alfred Holt refers to the 

 fact that specimens of this rare compound Ascidian collected off the Outer 

 Hebrides by Prof. Herdman have a green tint when alive, but change 

 into violet when placed in alcohol, and give the alcohol a green colour. 

 Natural violet specimens occasionally occur. The green colour probably 

 results from some chlorophyll-like body. So far as is known, it is not 

 due to chlorophyll in symbiotic Algas. The pigment cells are far 

 smaller than the algal cells in known cases of symbiosis. Moreover, 

 the Ascidian has been collected from 60 fathoms. 



The purple pigment is all but insoluble. Its behaviour resembles 

 that of the dibromindigo from Murex, and it is perhaps an isomer. It 

 also resembles that in Purpura and BonelUa. The experimental evidence 



* Proc. Roy. Soc, Series B, lxxxviii. (1914) pp. 227-36. 



