1892.] 



MICEOSCOPICAL JOUKNAL. 



189 



Nitzschia sigmoidea var. 



Navicula elliptica K. 



Navicula elegans Sm. var. avec les 



extremites capiiees. 

 Navicula formosa Greg. 

 Navicula fortis Greg. 

 Navicula interrupta K. 



No. 244. {Alai 

 Actinocjclus Barkleji Grun. 

 Actinoptychus undulatus var. 

 Amphiprora pulchra Baile}'. 

 Amphiprora maxima Greg. 

 Amphora Euleinsteinii Grun. var. 

 Coconeis scutellum E. 

 Coscinodiscus excentricus E. 

 Coscinodiscus ocuius iridis E. 

 Coscinodiscus radiatus E. 

 Cyclotella stylorum Br. 

 Epithemia musculus K. 

 Melosira Borreri Grev. 

 Navicula brevis Greg. var. elliptica. 

 Navicula cruciferum var. 

 Navicula elliptica K. 

 Navicula formosa Greg. 

 Navicula fusca var.? A. S. 7 f. 7. 

 Navicula humerosa Breb. 



Navicula major K. 

 Navicula peregrina E. et. varieties. 

 Navicula rhombica Greg. 

 Pleurosigma Balticum Sm. 

 Pleurosigma Terrjanum 11. P.* 

 Sjnedra pulchella K. 

 Triceratium alternans Bailey. 



sh*) South End. 

 Navicula interrupta K. 

 Navicula peregrina E. et var. 

 Navicula zosteretii Grun. 

 Nitzschia acuminata Sm. 

 Nitzschia scalaris Sm. 

 Nitzschia sigma Sm. 

 Nitzschia Tryblionella Grun. 

 Pleurosigma affine (jrun. 

 Pleurosigma balticum Sni. 

 Pleurosigma Americanum II. P.* 

 Pleurosigma delicatulum Sm. 

 Pleurosigma. Sp- n. intermediairc 



eutrc le PI. obliqunm Gyun. et la 



petite variete dti Sineude E. Sera 



iilterieurement decrit. 

 Pyxilla baltica Grun. 

 Surirella striatula Turpin. 

 Triceratium (Lithodesmimn) undu- 



latum E. 



Sectionizing Hydra Viridis. — About five years ago I tried 

 the experiment of growing the hydra from sections. I cut a hirge 

 and vigorous specimen into about ten pieces, and phiced them in 

 a small test-tube with water drawn from the household tap ; in 

 two or three weeks, eight out of the ten pieces had developed in 

 full-grown vigorous hydraj. Of course I was careful to exclude 

 all such things as cypris and cyclops, and everything that seemed 

 likely to prey upon the undeveloped sections, and also allowed 

 plenty of water, so that there was no risk of the oxygen becoming 

 exhausted, a rather important feature where animal life is con- 

 cerned, either in development or prolongation. — F. J. George^ 

 in Science- Gossip foi' August., i8g2. 



*By some error this is printed (Bristol) and P. Terryanum and P. Americamttn are trans- 

 posed, /-". Terryanum having been found only in the small pool before mentioned, from which 

 this " South End " gathering was taken. P Paradoxum was found in another gathering frdm 

 Morris creek, and many other forms appear in other gatherings beside those mentioned. 



I have sometimes been surprised to see old collectors, who should know better, attempt to 

 describe the diatomaCK of a section or a body of water from a single gathering. A fossil deposit 

 varies greatly in the varieties shown in diflerent strata, and even the same stratum will show a 

 collection of entirely different forms within a short distance of each other. 



The reason of this is easily seen by any one who studies the distribution of living forms. The 

 centre of a creek or inlet will generally show different varieties from those found on the margin, 

 and very different forms may be found on the margin of a pond within a few feet of each other. 



Some time since a friend sent me a sample of mud from one of the small lakes of Indiana ; it 

 contained abundance of P. attenuatum : wishing more, my friend sent me another sample 

 gathered by the same man from same place ; this had no Pleurosigma but was rich in Surirella 

 craticula. Wishing to study the relation between this and Navicula cuspidata, which was 

 also abundant, I sent for a third supply ; this did not contain a single specimen oi P. attenuatum 

 or 5. craticula, but N. Americana was plentiful, which did not appear in either of the other 

 gatherings. 



Bristol, Conn., May 20, iSg2. 



