42 



THE AMEEICi\]Sr MON^THLY 



[March, 



of swarm-spores in fig. 9 d and e. A 

 rapid revolving motion appeared in 

 the mass of swarm-spores as they be- 

 gan to form, increasing in intensity 

 as they grew, until finally they broke 

 away from each other. In breaking 

 away from each other, they 

 scattered in all directions, and 

 then it was seen that they had 

 two rather long cilia (fig. 9), 

 which were not previously 

 observed. They swam very 

 rapidly in a straight course, 

 pausing for an instant 

 with a jerk, and then resuming 

 their path again. Their color was 

 greenish. I should think there were 

 twelve or thirteen of these swarm- 

 spores in each mass, but owing to the 

 rapidity of their motions I could 

 not count them very correctly. 



The whole process of the formation 

 of the swarm-spores, from the first 

 appearance. of the mass of protoplasm 

 on the outside of the frond to their 

 final dispersion, did not occupy more 

 than fifteen or twenty minutes. 



The masses of protoplasm (fig. 9, b 

 and c) appeared on the surface of the 

 frond at irregular times and places, 

 two or three of the masses being seen 

 at once, no definite order seeming to 

 be observed in their production. 



Fig. 12. 



On the empty frond I counted thir- 

 teen of the points where the swarm- 

 spores had come out, and after they 

 had all gone it appeared to be quite 

 empty, nothing remaining in it but 

 some wrinkled, olive-green substance 

 It took the whole afternoon before 

 the frond was entirely empty. While 

 I was watching this desmid, a large 

 amoeba came gliding along and tried 

 to swallow it, and I thought my ob- 

 servations upon it were at an end, 

 but I was happily disappointed, for, 

 after having half enveloped it he gave 

 it up as being too large a morsel for 

 him. He took from it, however, two 

 or three of the masses of swarm- 

 spores that were developing at the 

 time, but three more bunches came 

 out afterwards, developed, and swam 

 away, the amoeba's digestion evi- 

 dently not being strong enough to af- 

 fect the inside of the frond. 



If any of the readers of this Jour- 

 nal have seen the same method of re- 

 production of Closteriu?n, and have 

 been more fortunate than myself in 

 following and watching the develop- 

 ment of the swarm-spores into the full- 

 formed Closterium, I would be glad 

 to hear from them. 



Manchester, N. H. 



Description of tlie Figures. 



Fig. 8. — Appearance of the Closterium 

 when first seen in the forenoon, with a ^-inch 

 objective. 



Fig. 9. — Appearance of the same in the 

 afternoon with the points {a a) and masses of 

 protoplasm {b c) that have just come through, 

 and the swarm-spores </and ^forming, j^-inch 

 objective. 



Fig. 10. — Point from one of the oval bo- 

 dies a, before the swami-spores have come out, 

 and some of the points left {e) after they have 

 gone, seen with the ^-immersion objective. 



Fig. 11. — The masses of protoplasm as seen 

 with the ^-objective, and a free swarm-spore. 



Fig. 12. — Appearance of ihe frond after 

 the swarm-spores had all gone. 



