16 



for months may not be seen. (Hydra, Daphnia, Plu- 

 matella, etc.) 



I have never found any larvae of insects, a not im- 

 possible circumstance, although so many millions are 

 living in the reservoirs. I only wish to remind you of 

 the myriads of Diptera, which on a fine Summer eve- 

 ning are swarming over the surface of the placid reser- 

 voirs, whose larvae live in the water only, breathing by 

 gills, after a certain time transforming into ''pupae," in 

 which the "imago" is developed. The most interest- 

 ing works on the development and histology of Diptera, 

 are August Weismann's, from whose lips I imbibed the 

 love of this interesting study.* 



The little wood -cut represents the ex- 

 ternal partf of an abdominal segment of M$kt*, 

 Cyclops with an encysted parasite, (600— |||nr <ir 

 700 diam.) which I several times observed. I lilll^l 

 I regret that I had no time then to prose- >■---- ''.'i J 

 cute any further inquiries to determine its 

 species, etc. fpF^ 



These little crustaceans, worms and 

 polyps occurring in the Croton water for themselves 

 alone, are not injurious, but when containing those en- 

 cysted parasites may spread intestinal worms. (Trema- 

 toda, Taeniada, Nematoda, etc. 



* Die Entwiklung der Dipteren, Leipzig, 1864, von Dr. A. Weismann, 

 Prof. d. Zoologie, Metamorphose der Corethra pi., von A. Weismann, Prof, 

 d. Zoologie in Freiburg in B. 



f Wood-cut Explanation. — w, external chitinnus body integument ; v, frac- 

 ture of the segment ; 8, encysted parasitical trematoda larva (?) 



N. B. — In the British Association for the Advancement of Science, held 

 at London, September 14 to 21, 1870, was discussed the " Spontaneous 

 Generation," and the " Spreading Agencies of Zymotic Diseases," by Hux- 

 ley, Frankland, Child, Samuelson and Calvert. Saumelson finally expressed 

 his opinion, resulting from experiments and observations which extended 

 over a long series of years, that those who prefer to adopt the theory of the 

 creation of living forms only from germs already in existence, would 

 eventually find their view to be correct. — I. London News. 



