F. A. PARSONS ON A NEW HYDROID POLYP. 127 



as there was no meeting of this Club last month, except the Gossip 

 night which I was unable to attend, I acted upon the suggestion, 

 and I am very glad that I did so, as it brought me a letter from 

 Mr. Bourne, in which he says : — " I am told by Mr. Charles 

 Stewart that you exhibited to the Microscopical Society a Hydroid 

 polyp, which Mr. Stewart informs me is the same as the one I 

 have lately described from the tank at Regent's Park. Mr. 

 Stewart further informed me that you had been for some time 

 acquainted with this form, and had found it in other localities 

 than in the Lily tank at the Botanic Gardens — if this is the case 

 it cannot be Limnocodium. I should feel greatly obliged if you 

 would let me have a line from you about it. I naturally considered 

 it in the highest degree probable that the thing was connected 

 with Limnocodium, but if it is not, and if it never developes 

 further than the condition in which we now see it, I regard it as 

 an even more interesting form, and should, of course, consider it 

 as your discovery." 



In reply to this letter I gave Mr. Bourne some information 

 about the polyp, and ventured to suggest that before coming to 

 the conclusion that it had no relationship to Limnocodium, it would 

 be well that the latter should be looked for in the tank in the 

 house for Medicinal and Economic plants, where it might have 

 easily escaped observation. 



I remarked just now that the polyps made their appearance on 

 the side of the sponge which had been in contact with the pipe. 

 This fact leads me to the inference that the polyps were developed 

 from germs contained in the water which I brought away with me, 

 for I do not see how they could have got there while the sponge 

 was alive ; moreover they were in different stages of development, 

 the earliest stage seen by me being a little mound of fuscous 

 coloured sarcode. Other specimens more advanced were similar, 

 but longer, the length varying, no doubt, in proportion to the 

 age of the individuals. When the polyp has attained its full 

 length, or perhaps a little earlier, its free end presents a warty 

 appearance due to a number of receptacles containing the urticating 

 thread cells. These thread-cells are very minute, the shape of 

 them being that of a very short cylinder with hemispherical ends. 

 The spines on the filament are not sufficiently distinct to be counted 

 under a quarter-inch objective — at least I was unable to count them 

 when I had them under examination with that power — but I was 



