466 ANIMAL NATURE OF DIATOME^E. 



50. STRIATELLA. Bacilli tabulati longitudinaliter 

 vittati ; vitttf pervice numerosce densae striceformes, stipes 

 lateralis. 



Though the only species of this genus (JS. unipunctata], 

 is common in the Adriatic, I confess myself unable to 

 form a clear idea of its structure. The complication it 

 presents in external appearance, and which is reproduced 

 in the figures of Kiitzing, seems to proceed from vittse of 

 the surface opposite to the one observed shin ing through; 

 there result from this, vittse, strongly and faintly marked, 

 alternating with each other. Does each one of these 

 vittse include a canal? And how far do they project 

 into. the cavity? The singular condition described and 

 figured by Kiitzing of smaller tablets (tavolette) attached 

 to larger ones, indicates a peculiarity of development, 

 which has no analogy in the remainder of the class. 



51. TESSELLA. 'Bacilli late tabulati, non concatenati, 

 dense longitudinaliter vittati; vittts medio interrupts 

 alternantes, stipes nuttus ? 



This genus, too, is reduced to a single species (T. 

 interruptd), and, therefore, it is impossible to judge of 

 the value of the characters that distinguish it from the 

 preceding or the succeeding, whilst we do not know the 

 organic importance or the true structure of the vittse. 

 The breadth of the tablets is remarkable, being five times 

 more than the length. There is frequently an absence 

 of a few vittse, accompanied at the same time by a 

 deformity or derangement of those contiguous. It 

 appears that this condition precedes the deduplication, 

 but we have no observation in point. It still remains, also, 

 to determine the figure of the lateral surfaces. 



52. HYALOSIRA. Bacilli tabulati quadrati, concate- 

 nati lateraliter stipitati, interrupte vittati; vittae alter- 

 nantes medio lineolis subtilissimis conjuncta. 



At first I was afraid that I was led, by want of skill in 

 observing, to believe that I could see in the two longer 



