366 Dr. H. M. Woodcock and Mr. G. Lapage. 



Loss of Syngamy and the Power to form Cysts. — We have discovered one very 

 interesting and important fact, however, which deserves to be mentioned. 

 By sub-culturing the flagellates* while they are still all in the active condi- 

 tion, i.e. before cysts have been developed, on to a fresh plate of the same 

 medium, we have found that multiplication will continue for a further 

 period (of two days or so), before conjugation sets in. The important fact, 

 however, is that, after a certain number of sub-cultures have been thus 

 made, the flagellates, although they are still able to thrive and multiply 

 actively on each successive transference, no longer undergo syngamy, followed 

 by cyst-formation, and have, so far as can be seen, entirely lost the power to 

 do so, at all events under the existing conditions.! Up to the present time 

 (October), we have thus kept a "strain" for more than 20 weeks, through 

 35 sub-cultures on to fresh " constant " medium, and in each sub-culture the 

 flagellates have multiplied enormously. In the sub-cultures up to the fourth 

 a very few isolated cysts were still found. But in none of the subsequent 

 ones has a single cyst ever been seen. The flagellates, instead of conjugating 

 and forming great numbers of cysts, as usual, degenerate and die off, only a 

 small proportion remaining still alive. Yet, at the end of 10 or 12 days, 

 sometimes more, a few individuals still persist alive, and the transference to 

 a fresh sub-culture can be successfully made. The flagellates which remain 

 alive are rounded, granular, very sluggish forms, with the flagellum sticking 

 straight out and almost motionless ; but, in the fresh medium, they are 

 capable of quick recuperation and renewed multiplication. 



During the earlier weeks, after this new strain was fahdy started, we never 

 observed any biflagellate forms, comparable to the conjugating pairs above 

 described, although thousands of individuals must have passed under our eyes. 

 Then, during the 8th and 9th weeks, respectively, we observed on two 

 occasions, in different observation preparations, a single biflagellate individual. 

 After this, we looked carefully for others, at intervals, but no more were seen 

 until the 14th week (in the 23rd sub-culture), when another was observed. 

 Since that time, in most of the sub-cultures, a few biflagellate individuals 

 (banner-like forms) have been found and the number of these has gradually 

 tended to become less infrequent, although they still constitute a very small 



* This experimental work, it may be mentioned, has been carried out upon another 

 species of Helkesimastiv, with which we have worked latterly. This form (H. major, 

 n. sp.) also occurs both in sheep and goats, and differs only from H. fcecicola in the larger 

 size of the adult individuals and also of the cysts, rendering it more convenient for study. 

 The life-cycle is similar- in both. 



t We tried the experiment of re-introducing the non-conjugating " strain " into the 

 original dung-culture (sterilised) with the object of seeing whether the ability to 

 undergo syngamy would be restored. This also gave negative results. 



