Notes on the Preceding Paper. 53 



charms. Indeed, iny delineation of the form of the disk rests 

 on a single individual, so that I do not attach the same cer- 

 tainty to it as to other features which I have observed ; and 

 the more, as I could not trace the marginal cilia at work. 

 Moreover, Mr. Slack has figured it of a very different shape. 



The entire height of an average specimen in its ordinary 

 state of extension is ^ of an inch ; of which the foot is 5*0^ 

 the body (from the cloaca to the base of the antenna), -a-g-n-th, 

 and the antenna j^th °f an inch. The case generally reaches 

 up to the cloaca. The greatest breadth of the body may be 

 about y^oth. 



NOTES ON THE PEECEDING PAPEE. 



BY HENRY JAMES SLACK, F.G.S. 



Mr. Gosse, in transmitting the observations in the preceding 

 paper, invited me to add any remarks, especially upon the 

 great discrepancy between his sketch and that which I pub- 

 lished in the ' ' Marvels of Pond Life," to which he has alluded. 

 However plainly a particular appearance might be presented 

 to my view, I should hesitate in adhering to its correctness in 

 opposition to so able an observer, if our opportunities had been 

 equal, but in this case I have had the advantage of repeated and 

 prolonged observations; while Mr. Gosse, even in the instance of 

 the " single individual," does not seem to have seen the disk 

 naturally expanded at all, and I conjecture his view of it must 

 have been taken under some peculiar circumstances — perhaps 

 of compression — which disguised its real form. I first dis- 

 covered the creature — which I cannot reconcile with the de- 

 scription given in Pritchard of the Cephalosiphon — in October, 

 1860, and from a single specimen gave an account of it, which 

 will be found in the Marvels of Pond Life. Upon receiving 

 from Mr. Gosse a note expressing his belief that the thing 

 might be a Cephalosiphon, although it was certainly not a 

 young Limnias, I endeavoured to obtain fresh specimens ; but 

 did not succeed till November, 1861, during which month I 

 sent a good many to him at Torquay. Some of them reached 

 that place alive, but from some cause (perhaps not liking the 

 air) not one expanded her disk as in Camden Town. As the 

 weed was abundant, and the creatures plentiful, in the Hamp- 

 stead pond, I saw no occasion to be in a hurry, and decided 

 not to call the attention of other naturalists to them until Mr. 



