[81] 



St^laiia ipalubosa* 



By a. Hammond, F.L.S. 



Plate 8. 



THE subject of this notice was brought to me a few weeks 

 ago by my friend Mr. Baily, who informed me that he 

 had witnessed the act of fission in a similar specimen a 

 day or two previously. The alleged reproduction of the Naid 

 worms by a process of fission, as I stated in a note on my paper 

 on Tubifex, received the most strenuous denial from Dr. Wil- 

 liams, the author of the report on the British Annelida.* After 

 quoting a statement by Professor Owen, to the effect that in this 

 very worm a proboscis shoots out from the posterior portion, 

 which is then detached from the parent worm, he says : — " On 

 the authority of hundreds of observations laboriously repeated at 

 every season of the year, the author of this report can declare 

 with deliberate firmness, that there is not one word of truth in the 

 above statement. It is because accounts so fabulous have been 

 rendered respectable by the fact that Professor Owen has thrown 

 over them the aegis of his great authority, that they demand a 

 contradiction, which may displease by the strength of the 

 language in which it is given." I had previously been led to 

 doubt the correctness of Dr. Williams' positive conclusion with 

 respect to Tubifex, and my doubt was confirmed upon seeing the 

 elaborate and exhaustive memoir by Bonnet of his experiments 

 upon these animals, — experiments which, it seemed to me, were 

 not to be lightly set aside. It was, therefore, with peculiar 

 pleasure that I heard from Mr. Baily his account of the fission 

 of Stylaria as witnessed by him, and received from him a spe- 

 cimen which I determined to watch. On the 24th February, the 

 worm presented the appearance shown in Plate 8, Fig. i, v/here 

 it will be observed that it possesses a long, fleshy proboscis, — 

 whereby it is distinguished from Nais, — and a pair of eye-spots. 

 A pharynx, or dilatation of the alimentary canal, immediately 

 succeeds the mouth, and the first three or four segments, includ- 

 ing the head, are devoid of bristles, a special feature of the Naid 

 tribe. We note again that the long filiform setse which adorn the 

 body are interrupted at about the posterior third of its length, 

 where a constriction occurs. The interruption, however, is more 

 apparent than real, for if examined under a ^-in. objective, the 

 integument of this portion is seen to bear a series of minute 

 * British Association Report for 1851, p. 247. 



