1921] NATURAL SCIENCES OF PHILADELPHIA. ]43 



tion, and, behind, it is drawn out into a point, itself continued in 

 a very thin thread, whose length may be nearly double that of the 

 fusiform body (Lauterborn calculates it to 12[jl; but I have seen 

 it attain 30[jl and more), and which attaches by its extremity far 

 away on some point of the inner surface of the tube. This attach- 

 ing filament is highly retractile, and from time to time draws the 

 animalcule very far inside the tube. Its normal position is at some 

 little distance from the opening. In the anterior part of the body 

 is seen the chromatophore, a golden-brown lamina, but which only 

 appears distinct on one of its sides, where it is seen double becauses 

 of its recurving there on itself. Sometimes it looks broken in its 

 middle, and the appearance is that of two rods joining each other 

 at an angle. At its anterior extremity is a very small, but distinct 

 stigma. In the same part of the body is a small contractile vesicle 

 (Lauterborn found two), and behind the chromatophore lies gener- 

 ally a large, egg-shaped mass' of leucosine; in the very pure and 

 transparent plasma, tiny shining granules are disseminated; a very 

 pale globular nucleus, with a small central caryosom, occupies the 

 middle of the body, being mostly very indistinct on account of the 

 chromatophore, in the folds of which it is lost. From the slight 

 notch that is seen at the anterior extremity, two flagella arise; one 

 of them, the principal one, about as long as the body, swings in 

 rapid longitudinal vibrations, while the other, the accessory fla- 

 gellum, only 5 or Q\x in length, remains motionless at an angle of 

 35" to the former. 



A little further consideration is necessary as to the systematic 

 position of this small organism. Lauterborn did not unhesitatingly 

 propose this Flagellate as new. As far back as 1890, Imhof (18) had 

 described, with the name of Dinohryan huetschlii — but in a few 

 words only, and without any accompanying figure — a small Flagel- 

 late, very similar indeed to Lauterborn's Hyalobryon, but in this 

 form the tubes are expressly stated to be set one within another, 

 and nothing is said of the characteristic "rings of growth. ^^ 



The form I studied also looks rather different from Lauterborn's 

 Hyalobryon, and this typical insertion of the tubes, in place of Lauter- 

 born's "rings of growth," would seem to indicate another species, 

 perhaps Imhof's Dinohryon buetschlii? But Imhof insists on 

 the fact that in his Dinohryon "the anterior third part of the tube 

 grows gradually narrower, down to one -third of the diameter next to 

 the opening," while nothing of the sort is to be seen in Hyalobryon as 

 I could verify in hundreds of specimens. Perhaps a third species 



"Stokes' Epipyxis socialis (34), which presents some hkeness to Hyalobryon, 

 seems to me, even more perhaps than to Lauterborn, very different from Hyal. 

 ramosum. 



