1921] NATURAL SCIENCES OF PHILADELPHIA. 141 



even the outlines of the colonies; as a rule one sees only the numerous 

 golden-brown Flagellates, placed next to each other, without its 

 being possible to decide how they are arranged." 



" Hyalohryon constitutes, like the well-known Dinobryon, tree- 

 like or brush-like colonies, but which, different from the latter 

 genus, do not swim freely about, but are fixed on water-plants or 

 any other substratum. The number of the individuals united into 

 a colony is very variable and sometimes goes to a hundred. Like 

 Dmohryon the Flagellates inhabit special capsules, which here are 

 of a tubular form and often are more or less, even strongly, bent; 

 the basal extremity terminates in a short cone. Towards the an- 

 terior end, the tubes become somewhat narrower, and at their bor- 

 der look finely toothed. This apparent denticulation is due to 

 the fact that the Flagellates, which always stand near the aperture 

 of their capsule, periodically leave here a deposit in the shape of 

 new rings of growth, on the inside of the somewhat enlarged border. 

 As the process is often repeated, the tubes lengthen more and 

 more; and many of them are seen, whose anterior part is formed 

 of ten and more rings, resting cup-like in each other." 



My observations are such as to confirm in a general way those 

 of Lauterborn, but the accordance is not complete in some of the 

 details. In the Hyalohryon I had the tubes were never nar- 

 rowed near the summit; on the contrary, they were perfectly 

 cylindrical up to very near their distal extremity, where they some- 

 what expanded (Plate VIII, fig. 50) instead of narrowing. Lauter- 

 born's "Anwachsringe," or so-called "lines of growth," were mostly 

 absent; sometimes, however, they were present, either on some of 

 the members of the colony, or more rarely on nearly all of them, 

 but they could in no case be considered as rings of growth; they 

 were tubes, set in each other, each of them of some length (Plate 

 VIII, fig. 54). There was even no difficulty in ascertaining the 

 manner in which the construction had been accomplished; little 

 Flagellates approaching had undoubtedly become attached just 

 inside an empty tube, very near the opening and on one side only 

 of the wall, then they grew up, forming first a whistle-like, then a 

 regular, tube. Plate VIII, figure 54, shows this special arrange- 

 ment of the new tubes inside the old ones, and at the top is seen, 

 in the form of a simple sharp scale, the beginning of a tube whose 

 construction was not continued, the Flagellate having, it must be 

 supposed, left the place very soon after finding it. 



It would then be necessary to modify the terms used by Lauter- 



