Journal of Applied Microscopy. 



587 



plastic stem. Of the general effect of varying atmospheric conditions also, the 

 student will gain information in the field, and nowhere else. The marvelous 

 work done by Fries in this group and among the fungi in general, was due to the 

 circumstance that he studied these things in their haunts, and so, even without 

 much aid from the microscope, as we count microscopes now, effected in classi- 

 fication much that will abide forever. On the further study of slime moulds in 

 fruit we may speak later. 



Thomas H. Macbride. 

 University of Iowa. 



On the Action of Methylen Blue on the Thread-Cells of Living 

 Specimens of Hydra Fusca. 



A few days since I felt desirous of testing the influence of methylen blue on 

 living Hydra, and having a good supply of healthy specimens, made the experi- 

 ment. I first made a weak solution of the stain by taking a small amount of the 

 Bx stain of Gruebler and mixing it in hydrant water till the latter, passing through 

 a faint blue color, reached a dark but still transparent tinge. I then dropped my 

 Hydra in the solution and after a moment examined it with a low power. I was 

 very much surprised to find that the tips of the tentacles were entangled with 

 what seemed to be threads of wool. I could not see where the wool had come 

 from, and I soon saw that it was not wool at all, but that at the base of each 

 thread was a swelling imbedded in the ecto- 

 derm, and that the animal, perhaps from the 

 irritation of the chemical, had discharged 

 multitudes of the nematocysts, whose threads 

 had at once become deeply colored. Soon 

 this condition, which at first affected the tips 

 of the tentacles, spread to their proximal ends, 

 and aflected also the body, threads being 

 visible sticking out from the hypostome (Hy. 

 in fig.) and also from the side walls. 



Many of the threads were wholly separated 

 from their insertion in the animal, and could be seen floating isolated in the 

 water. Two kinds are clearly demonstrated by the method ; viz., the larger 

 barbed cells, and a second much smaller barbless kind. The two are also 

 clearly visible /// situ in face views of the tentacle, under the high power after 

 staining. In these two types, 1 noticed that the thread is much thicker and 

 shorter in the smaller type, and more delicate in the larger barbed kind. At 

 the inner ends of both kinds of isolated nematocysts the remains of the cell are 

 visible in many cases, and in this can be seen a well-stained nucleus. 



H. L. OSBORN. 



Hamline University, St. Paul, Minn. 



