452 0. CLIFFOKD DOBELL. 



closely corresponding with that depicted in PI. 27, fig. 1. 

 This shape may therefore be considered as " normaL" The 

 length varies from about 8 ju to 17 /a, an average-sized 

 animal being about 14 /n. At the anterior end [see PI. 27, 

 fig. 1] ai'e inserted three anteriorly directed flagella, in 

 length about one and a quarter times that of the body. From 

 the same basis arises another and longer flagellum, which is 

 directed backwards (Schleppgeissel). The spot from which 

 these flagella arise appears in the living animal as a refrac- 

 tive granule, situated immediately above the nucleus, which 

 is placed anteriorly. In stained preparations this basal 

 granule is seen to be composed of a chromatic substance 

 which staius like the nucleus. Punning through the whole 

 length of the body of the animal is a somewhat flexible axial 

 rod (Achsenstab), which terminates anteriorly in the basal 

 granule of the flagella, and posteriorly is drawn out into the 

 caudal process of the body. The axial rod either traverses 

 the nucleus, in order to reach the base of the flagella, or else 

 lies in close contact with it. It is impossible to be quite 

 certain of the exact relationships of these structures. The 

 rod is, I believe, skeletal in function. Its general aspect 

 and relations to the nucleus recall the axial rods of the 

 pseudopodia of the Heliozoa. Near the base of the flagella 

 is to be seen a Avell-marked cell mouth or cytostome. 



The creatures exhibit great activity of movement, which 

 does not appear to be affected in the very least by light, as is 

 the case with some flagellates. Warming appears to increase 

 their activity, but no critical experiments on the efi^ects of 

 temperature were made. The food consists of the small 

 micro-organisms abounding in the medium. 



Division. — Division is, as inmost flagellates, longitudinal, 

 and presents certain features of interest. Briefly, the pro- 

 cess is as follows [see PI. 27, figs. 2 — 10] : — An ordinary 

 individual [fig. 2] becomes more or less globular [fig. 3]. 

 At the same time the axial rod is absorbed, that is to say, it 

 disappears. The flagella are now seen as a very rapidly 

 vibrating bunch, springing from a refringent spot — the 



