200 W. ARCIIKR. 



that experienced observer and enviably excellent draughts- 

 man had already described a form' under the name 

 of Blffiugia ligata, which certainly belongs here, and which 

 extremely probably is identical with either one or other 

 of the forms referable to Hyalosphenia (or, indeed, these, 

 nay, all three, may be possibly found to be identical 

 when better known). Stein's description (1854), unaccom- 

 panied by any figure, is too brief to judge by; but 

 if Tatem's form coincides with Schulze's that should, 

 without doubt, be denominated Hyalosphenia ligata, 

 (Tatem), Schulze. If, on the other hand, it coincides with 

 Stein's, it would be but a synonym Qi Hijalosphenia cuneata. 

 Stein. In a letter to me iNIr. Tatem remarks that he cannot 

 regard the difference of the test sufficient to remove such a 

 form from Diffiugia. In this I cannot agree with him. Sin- 

 gularly enough, it is since I last wrote that I had an oppor- 

 tunity to see my first Hyalosphenia ; it quite agreed with 

 Tatem's excellent figure in the main, except in two points : 

 first, in that my example was just one half the linear dimen- 

 sions of his (being ^^o" long in place of -^^77") ; and, second, 

 that it shows (what is not delineated by him) a distinctly 

 nucleolated nucleus, posed as usual at about the posterior 

 third of the body. The four stolon-like sarcodic prolonga- 

 tions by which the body-mass was attached to the inner pos- 

 terior surface of the test were quite as he shows them. But 

 in this circumstance the form is not singular, many other 

 rhizopods showing them in greater or less number. In my 

 example the single lobose (scarcely branching) pseudopodium 

 was also characteristic. Surely, indeed, there must be deep- 

 seated and inherent " generic" differences between those 

 groups of forms {genera, in my sense) which wholly eschew 

 all extraneous aid in the build-up of their tests, which are 

 a pure secretion product only, and other groups of forms 

 which, with a marvellous power of selection and adap- 

 tation, must "cast about" to alight upon suitable building 

 material ; nay, with what " specific" uniformity one such form 

 sticks about it those foreign " stones," of the most rugged 

 character, in the most rugged fashion, whilst another chooses 

 very much smoother ones, and seemingly lays them on with 

 what, by comparison, may be called "mosaic" regularity. 

 And so on. Again, surely the hyaline continuous membrane- 

 like test of Hyalosphenia is quite a different thing from that 

 of Quadrula, composed of, as it were, distinct panes of glass, 

 coherent by their margins in such a way a.s to build up and 



* ' Monthly Microscopical Jourual,' vol. iv, p. 313, t. Ixviii, f. 1. 



