102 



SCIENCE-GOSSIP. 



whose wants Divine Providence has not overlooked. 

 Their affinities in nature are with the diatoms and 

 certain species of alga?. 



We only intend speaking of the commoner forms, 

 which, fortunately for our friends, are inferior to 

 none in beauty, and afford to all microscopists, 

 young and old, the greatest pleasure, and ample 

 scope for the use of the highest and most perfect 

 powers in their examination. 



Fig. 95. Closterium sti-io/attim Fig. 94. Ctoslerium Leibleinii 

 X 250. X 250. 



One of the most common bears the name of 

 Closterium. The various species, of which Pritchard 

 mentions some thirty-six, or thereabouts, are more 

 or less crescent- shaped — some being nearly straight, 

 and others curved like the new moon. The surface 

 in general is smooth, but there are many examples 

 of its being delicately striated. At each end of the 

 frond there is a "terminal clear space, in which 

 are active granules." These require a 5-glass to 

 show their extraordinary dancing movements, as if 

 each had an independent, merry existence. 



With bright illumination (and$-obj.) one may see, 

 just beneath the surface, that the particles of enclo- 

 chrome are seldom stationary, but in general move 

 steadily up or down the frond, and no difficulty will 

 be experienced in following with the eye the course 

 of the circulation at the edges, where some have 

 asserted they have seen cilia. We have never seen 



[May 1, 1866. 



this, but our examinations have not been careful to 

 the degree which the observers referred to insist 

 upon. Pritchard seems to think there is a possi- 

 bility of an optical delusion.® While looking at 

 these organisms, they will be observed to move 

 slightly, but the means by which this is effected 

 have, as yet, eluded detection. 



The other evening I saw the end of a bright-green 

 Closterium seized by a large animalcule, Notommata 

 myrmeleo (?) and subjected to the action of the 

 teeth. Soon, I found that the particles of chloro- 

 phyll were leaving the desmid, and passing down 

 the gullet of the animalcule, evidently by suction, 

 and I watched them with great interest; firstly, 

 because I never before saw a rotifer taking a salad 

 in so civilized a manner (for they generally transfer 

 their vegetable diet into their crops by a rapid jerk, 

 particularly when it is small enough to go down 

 whole) ; and, secondly, because apertures at the 

 ends of the frond are not generally believed in. 

 When the animalcule had finished its supper, that 

 is to say, when every particle of nutriment was 

 extracted, it cast the empty frond among others 

 that were strewed about, and I could not detect the 

 slightest rupture in the delicate transparent case 

 which a few moments before was so full of green 

 contents. There may have been one nevertheless. 



Fig, 96. End of frond of Closterium lunula (showing active 

 granules in chamber at the end ; the arrows indicate the 

 directions of the surface circulation) x 500. 



The mode of reproduction in Closteria is twofold 

 (?), by self-division and by conjugation. In every 

 frond of Closterium will be noticed a central clear 

 space, dividing it into two segments. Here a 

 gradual separation takes place, occupying some 

 hours before it is completed. The separated halves 

 then each commence to grow independently, till 

 ultimately a copy of the parent form is assumed. 

 This is an outline of self-division. Conjugation is a 

 different process ; two individuals approach each 

 other and come into contact. They then intermingle 

 their green contents and a curious globular f body 



* Other authors deny the existence of cilia in the desmids 

 altogether, 

 t Not globular in all desmids. 



