1890.] MICKOSOOriCAL JOUKNAI... 283 



. 



green. The leaves liave, of course, entirely withered and fallen, the 

 tendrils are dry and hard, as is also a portion of the stem at each end, 

 but in the central portion the barU is green, and, with the wood, has 

 every appearance of being fresh tissue. 



Experiments on Hydra, recently conducted 1)y Dr. C. Ischikawa, 

 show that the oft-cjuoted experiments of inverting the body tube of hydra 

 need to be explained more fully. He finds that the ectoderm cells do 

 not become endoderm cells, but the hydra either resimies its former 

 position or dies. When the body is cut in two, a new mouth is formed 

 bv the folding over of the ectoderm cells. 



Fresh-water Algge. — Prof. William West contributes to the June 

 number of the yoiirnal of the Royal Microscopical Society an article 

 on the Fresh-water Alg;e of North Wales, read by him at the meeting 

 of the Society, April i6, 1S90. The paper gives a list of the species 

 found by the author, and not included in the previous list of Mr. A. W. 

 Wills, published in i88r, and such of that list as are found in new 

 localities. 



Diatoms. — Mr. Cornelius Onderdonk {Microscope^ y.^ 22^) has ex- 

 perimented to ascertain the cause of the motion of diatoms. Believing 

 that neither the theory that invisible cilia, not streams of water pouring 

 through the frustule, were the cause of the motion, he stained fresh 

 diatoms with methyl green and found that the fiustule w^as surrounded 

 by a very delicate layer of protoplasm which he calls a mantle, and 

 gives ^-o/ro77 of an inch as its greatest thickness. The mobility of pro- 

 toplasm, as manifested in other plants, he thinks sufficient to cause the 

 motion of the diatom, which he says only occurs when the diatom is in 

 contact with some other body heavier than itself, otherwise the object 

 is moved. The diatom giving the best results was Pinnularia radiosa. 



Pollen. — Prof. Byron D. Halsted has shown {Microscope, x, 239) 

 that the pollen of green milkw^eed {Asclepias viridijforztiji) can be in- 

 duced to germinate between sheets of agar agar so thin that the pollen 

 tubes can be studied through the films with low' powers of the micro- 

 scope. The species of the allied genus Asclepias give similar results, 

 and the experiments are certainly sufficiently interesting to be often re- 

 peated by workers with the microscope. 



Cell Nucleus. — Experiments by Dr. B. Hofer {Jahr. Zeit.f. Nat.,, 

 xxiv, 105) show that the mobility of protoplasm is dependent upon 

 the nucleus of the cell, and that digestive fluids are only secreted by 

 protoplasm in which the nucleus exists, while respiration and the func- 

 tion of the pulsating vacuole are not dependent upon the presence of 

 the nucleus. 



Striped Muscular Fibre. — Mr. C. F. Marshall finds that the trans- 

 verse stria' of-»voluntary muscular fibres are directly connected with the 

 muscle corpuscles and that this network is connected with the nerve 

 endings. 



Ancestry of Insects. — The Jotirnal of the Royal JS Hero. Society 

 quotes E. Haase as urging that the researches of various observers 

 ''justifies the supposition that the existing hexapoda are to be derived 

 from polypodous myriapodiform ancestors." These suggestions are 

 based upon facts which we now know in regard to the abdominal legs 

 of the larval staee. 



