INTRODUCTION. 33 



this minutely granular matter, larger granules, or rather 

 vesicles, make their appearance. These Ehrenberg calls 

 ova ; but I cannot perceive the slightest difference between 

 them and the granules present in the higher Algse. 



On applying diluted tincture of iodine to different species 

 of the Desmidiese, the granules become very dark with a 

 purplish tinge showing the presence of starch. When the 

 tincture of iodine is used in its undiluted state, the colouring 

 matter becomes nearly black and conceals the bluish tint ; 

 in some specimens too this tint is hardly perceptible, whilst 

 in others it is very apparent. In no instance have I found 

 the presence of starch indicated unless granules were pre- 

 sent, as the fluid colouring-matter always becomes brownish. 

 The application of iodine to Conjugatee in different stages of 

 growth was followed by a precisely similar result. In the 

 young plant no starch was detected, but the colouring matter 

 changed to an orange-brow^n. On the other hand, in the 

 conjugating filaments the granules became blue, and the 

 sporangia especially acquired the very dark colour observed 

 in the Desmidiese, and did not exhibit the iodide of starch 

 until they were crushed. 



Professor Bailey's testimony is the more satisfactory be- 

 cause it is not the evidence of a partisan, but the admission 

 of one inclined to regard the Desmidiese as pertaining to the 

 animal kingdom. Although he does not " consider the pre- 

 sence of starch in these bodies as conclusive evidence that 

 they are plants," yet as a professor of chemistry he is aware 

 that starch is not an animal product, and he suggests there- 

 fore, with some ingenuity, "Is it not possible that they are 

 animals which feed, wholly or in part, on amylaceous matter 

 extracted from the aquatic plants among which they live ? 

 if so, the detection of starch in their stomachs is not sur- 

 prising." 



In the young cell there is no starch, but after its first ap- 

 pearance it continues to increase and is most plentiful in the 

 sporangium ; facts quite incompatible with Professor Bailey's 



D 



