Sketch of the Infusoria of the family Bacillaria. 301 



en in the above extract, agrees exactly with what I have seen in 

 several species. The currents are very distinct, so much so, in 

 fact, that they attracted my attention before I was aware that 

 they had been noticed by others. 



5th. Action of Iodine. — I cannot otherwise account for Mr. 

 Dalrymple's statement that iodine " in no instance produced in 

 the Closteria, the violet or blue color indicating starch," than by 

 supposing that the specimens he examined were not in the proper 

 state to exhibit it. Meyen expressly states, that it is "at certain 

 times, particularly in spring," that the starch may be detected. 



I am able by conclusive experiments to confrm Meyen's state- 

 ments as to the presence of starch in these bodies. In specimens 

 gathered in November, many of which I have still by me in a 

 living state, 1 find no difficulty in producing the blue or purple 

 color with tincture of iodine. Sometimes, however, the speci- 

 men becomes so opaque by the action of this reagent, that the 

 purple color of the grannies can only be detected after crushing 

 the specimen by means of the compressor. The characteristic 

 color of iodide of starch is then shoicn most distinctly. T have 

 repeatedly treated in this way the large species, C. trabecula (fig. 

 32, PI. 1) as well as others, and have uniformly found that a por- 

 tion of the interior takes the blue or purple color. 



I cannot however consider the presence of starch in these bod- 

 ies as conclusive evidence that they are plants. Is it not possible 

 that they are animals which feed, wholly or in part, on amyla- 

 ceous matter extracted from the aquatic plants among which 

 they live ? If so, the detection of starch in their stomachs is 

 not surprising. 



6th. Organs of motion and moving papillce. — These I have 

 not yet seen, but do not feel authorized to deny their existence, 

 as I am well aware that my microscope,* although a very good 

 one, is probably inferior to the one used by Ehrenberg. It shows 

 the lines on the scales of Podura as well as I have been able to 

 see them by any instruments in this country, yet I have not suf- 

 ficient confidence in its power, or my skill in using it, to contra- 

 dict the statements of results obtained by so distinguished an ob- 

 server as Ehrenberg, in using the best instruments of Europe. I 

 can vouch very positively for what I have seen, but will not pre- 

 tend that more may not be seen by others. 



* Made by Cliarles Chevalier, 130 Palais Royal, Paris. 



