22 EUCRATIID^. 



Polvzoon which he had o])tained at Tenbv, and named H. 

 fragilis ; and Norman has since identified this form with S. 

 clavata, and has suppressed Dyster^s specific name in favour 

 of mine*. 0£ course, if this decision were well-founded, 

 the present genus would be wholly superfluous. 



I am quite unable, however, to adopt the opinion of my 

 friend Mr. Norman in this case. H. fragilis and S. clavata 

 are, as I shall show, perfectly distinct forms, and, so far as 

 our imperfect knowledge of the former will enable us to 

 judge, are properly referred to different generic groups. 



Dy sterns description of his Huxley a fragilis would be 

 more satisfactory if it were more minute ; but the shape of 

 the aperture, which, we are told, is "rounded or semicir- 

 cular above, and straight below/' separates the species 

 which he had in view conclusively from S. clavata. It is 

 also noticeable that his account of the mode in which the 

 cells are connected could hardly have been suggested by 

 the latter. 



We have other important evidence to the same efl'ect in 

 the drawings of the two forms from Mr. Busk^s accurate 

 pencil, published in the ' Microscopical Journal.^ It is 

 only necessary to compare the figures of Scruparia clavata 

 in the fifth volume of the Journal (plate xvii. figs. 5-8) 

 with that of H. fragilis, taken from Mr. Dyster's specimen, 

 in the sixth volume (plate xxi. fig. 1), to be convinced that 

 the originals were at least specifically distinct. Not only 

 the shape of the aperture, but its size and position are 

 shown by these figures to be different in the two forms, 

 whilst there is also a striking dissimilarity in the charac- 

 ters of the cell itself, and in the mode of branching. We 

 have, then, two species to deal with. 



As to the question of genus, if the principles which I 



* Quart. Journ. Microsc. Sc. ii. s. viii. p. 212. 



