1905.] NATURAL SCIEN'CES OF PHILADELPHIA. 667 



combination through the water is then erratic beyond what is usual. 

 Loricae occur, also, with duplicate apertures, though whether such are 

 due to a similar state of affairs, only more prolonged, may be matter of 

 doubt. Sporulation, or the splitting up of the whole monad into a 

 multitude of very small, monoflagellate spores, which has been observed 

 in this as well as in other genera of the Protozoa, is evidently a less 

 frequent phenomenon. The evidence of it, however, is often seen in 

 the numerous very small loricae of many shapes. These small loricae 

 cannot with any certainty be referred to species, since in them the 

 sjiecific features are to a large extent undeveloped. The different steps 

 of the process that results at last in a fully developed monad, starting 

 from these spores, would seem not to have been followed by students. 

 It is evident, however, that the steps are few; since while very small 

 loricae are common, medium-sized ones are comparatively rare. 

 Authors have endeavored, and generally with success, to confine their 

 descriptions in this genus to mature forms. The specific characters 

 being almost without exception founded on the shape, size and surface 

 markings of the loricae, it is at once evident that for specific diagnosis 

 these loricae should be fully formed. It would seem, however, that in a 

 few cases this principle has not been in operation to the fullest extent 

 possible, and a few species are in consequence not quite adequately 

 ciiaracterized. In the descriptive part that follows, only the loricae 

 that are mature, as manifested by their full development in point of 

 color, size and markings, are accepted as typical. 



All the species of Trachelomonas known to the writer are found in 

 fresh water. Roadside pools, ditches, ponds, all yield them in larger 

 or smaller numbers. They congregate in particular around rusty 

 patches where ferrous compounds oozing out of the soil are in process 

 of oxidation and precipitation. They often abomid, however, in still 

 waters covered with Lemna, and in those filled with Utricidaria, Pota- 

 mogeton and other aquatics. 



Klebs has described^ two forms of Trachelomonas that are devoid 

 of chlorophyll, one of which he has named T. reticulata and the other 

 7\ volvocina var. hyalina. Both occur in decaying organic solutions, 

 and are no doubt of saprophytic habit. Neither of these appears to 

 have been noted in the territory covered by this paper. 



In the table of species all the well-known forms are given whether 

 known in Delaware Valley or not. A single form, not considered of 

 specific value, is distinguished by an asterisk. 



* Klebs, Untersuch. Tubing. Inst., I, 1883. 



