280 



backwards, whilst the others were moving forwards, and at 

 such times the tube does not stretch to accommodate the 

 crowding, but yet is often bent by the force of the moving 

 frustules. In fact this force must be considerable, as is 

 evidenced by the size of the obstacles, as grains of sand, 

 which a small Diatom will move; and in CoUetonema I have 

 seen the tough tube membrane bent inwards so as almost to 

 collapse by such a crowding as I have mentioned. 



As I have mentioned Mr. Kitten's paper in ' Science 

 Gossip,' I must here take the opportunity of saying some- 

 thing in regard to that article, and I feel sure that he Avill 

 not take amiss what I shall say when he understands the 

 spirit in Avhich it is written. 



First, I wish it to be understood that the specimens and 

 the letter accompanying them were sent to Dr. Arnott for his 

 opinion ; thereafter I intended to publish the facts treated of 

 myself. However, as Mr. Kitton has made public his 

 opinions on the specimens, I Avill now give mine ; but the 

 fact of its being a private letter of mine from Avliich he 

 quotes, and one never meant to be made public, nuxst explain 

 what I there say. He has considered the " queer form " to be 

 a new Fragillaria, and has named it crotonensis. Evidently 

 he does not agree with tliat portion of my letter which he 

 quotes, when 1 say: "I am not in favour of naming forms 

 after places or persons, but strongly incline to distinctive and 

 descriptive names." If the form were a new species I should 

 have named it myself; but Dr. Arnott at once said it was 

 likely to be FrayiUaria capuchia, var. y, and such I see 

 Mr. Roper points it out to be in the July number of the same 

 periodicaL 



As it may be of interest in connection with this point, 

 I may say that in a previous specimen of the sediment from 

 the Croton water which I had sent him, Dr. Arnott informed 

 me he had found the following species : — Ctjmatopleura 

 eUiptica, Navicula triaodis, and gibberula, Surire/la craticula, 

 Deyiticulu obtusa, Epithemia zebrina, Cocconeis Thwaitesii, 

 Achnaiithes ventricosa, Cyclotella rotula and operculata, 

 Orthosira orichalcea, Gomphonema tcnellum, and another 

 intermediate between dichotomum and intricutum, most likely 

 the latter. 



