154 The Scottish Naturalist. 



larger ; while in the Mesocarpece the contrary is the case. 2. That 

 the portion of the conjugating canal contributed by the germ-cell is 

 shorter and wider than that contributed by the sperm-cell. 3. That 

 the protoplasmic contents of the cells always travel in one direction, 

 that is, that in scalariform conjugation the contents of the cells of one 

 thread invariably pass over into the cells of the other thread with 

 which it is conjugating ; and 4. That in Mesocarpus the spore which 

 is formed in the conjugating canal never occupies its centre, except 

 in those cases where the spore is large enough to occupy the whole 

 of that space. My valued friend, Mr. F. Bates, of Leicester, answered 

 Mr. Bennett in a paper in " The Journal of the Quckett Mic. Club" in 

 a manner so entirely in agreement with my own observations, that I 

 have no hesitation in adopting the reply as expressing my own con- 

 clusions. He shows convincingly, as I think, that the points Mr. 

 Bennett relies on to prove his case are untenable. The paper will 

 be found in the part for March, 1885. Microscopists will learn with 

 regret that Mr. Bates has been obliged to give up the use of the 

 microscope. 



Another exceedingly interesting group of the Fresh-Water Algse is 

 the CEdogoniece. Since the investigation of these plants was put on 

 a proper footing by Pringsheim, several years ago, they have been 

 assiduously studied ; and by no one more carefully than by Professor 

 Wittrock, whose monograph is the standard work on the subject. 

 Not much, I am sorry to say, towards the investigation of the species 

 comprised in the two genera, (Edogonium and Bidhochcete, has been 

 done in the district embraced by the Union ; indeed, I do not know 

 of any observations prior to my own ; and mine are necessarily very 

 fragmentary, and do not represent more than half the species found 

 in Scandinavia, while, I feel sure, the numbers in the two countries 

 should be nearly equal. Any one taking up the study of this beauti- 

 ful family would enter upon a practically unoccupied field ; and 

 numerous interesting discoveries would reward his labours. 



I -return to the Conjugates for the purpose of making a few remarks 

 on a remarkable division of that large and important order, one to 

 which I have devoted a little attention, viz., the Desmidicw. These 

 elegant objects, I need hardly say, are very minute, the very largest 

 of them being just barely visible to a sharp eye as a green point; and, 

 therefore, fairly high magnifying powers are required for satisfactorily 

 working them out. I may remind you that they are unicellular 

 Algse : i.e., each individual consists of a single cell, usually more or 

 less deeply constricted in the middle, and having its halves perfectly 

 symmetrical. The surface is often highly ornate. It is usually 



