ARTIFICIAL SEA-WATEE. 269 



confinement (such, for instance, as Nos. 27 to 32), 

 even under the most advantageous circumstances of 

 space, had their existence more prolonged with me ; I 

 would merely state, that I have met with no more 

 difficulties with the artificial than with the actual sea- 

 water, under the same conditions. ISTos. 1 (this is 

 now m the gravid state represented in ' Johnston's 

 Zoophytes,' plate 1), 2, and 16, made their appearance 

 spontaneously, as it were, on some empty shells and 

 other debris placed in the water six months before, 

 which had not been changed during the whole of that 

 period. Nos. 3 and 5 to 10 are very hardy with me; 

 but No. 4 is, in general, precarious. Nos. 13, 14, 15, 

 lived in a quart jar for three months ; at the end of 

 which time I disposed of them, after they had added 

 hundreds of new cells to the polypidoms. Nos. 19, 

 20, 21, added considerably to their tubes; the new 

 portion being indicated in No. 20 by its superior 

 whiteness, and the rate of increase being about a third 

 of an inch in six months. On the 1st of May, I 

 counted ten young of this species, the parents having 

 been in my possession since September 4. Colonies 

 of No. 23 are very vigorous and active ; but I find that 

 they have a period of rest from soon after midnight 

 to about 4 or 5 P.M. 



" Many of the Actimce, mentioned in the above list, 

 are the same individuals which I had at the com- 

 mencement of my experiments, and most of them 

 have brought forth young abundantly. The deve- 

 lopment of Nos. 16 (this especially), 17, 18, have 

 afforded me many weeks of most interesting observa- 

 tion. In Nos. 39 and 40 I have noticed that 



