138 Prof. H. James-Clark on the Spongi^e ciliata3 



contracts so vigorously and abruptly, at the rate of six times a 

 minute^ that there seems to be a quite sensible shock over that 

 side of the body in which it is imbedded. 



The re])roductive organ may possibly be represented by the 

 very conspicuous, bright, highly refracting, colourless, oil-like 

 globule (w), which is enclosed in a clear vesicle, and appears 

 to be so constantly present in the depths of the posterior third 

 of the body. Its position seems to be invariably on that side 

 of the transverse axial plane which is opposite to that in which 

 the contractile vesicle {cv) lies. Nothing fm-ther of a positive 

 nature can be said in regard to this body ; but we may con- 

 jecture that, inasmuch as it cannot well be assigned to any 

 other office, not even to that of an eye-spot, it is in all proba- 

 bility an organ of reproduction. 



In regard to the stem (fig. 3,^:»c?), it may be added that, 

 although it appears to be of the simplest nature — a mere 

 gossamer thread as it were, it is none the less positive, as a 

 support, than that oi Anthophysa (figs. 47, 48, 49, ^c?), and 

 must indeed possess a similar self-reliant power in order to 

 keep the body in the same relative position in regard to the 

 object to which it is attached, or to sustain it in an upright 

 attitude at a time when the flagellum is quiet and there is 

 consequently no other means of preventing the animal from 

 sinking down upon the nearest fixed point. 



§ 2. Monas neglecta^ nov. sp. PL V. figs. 5, 5*, 5^, 6. 



To a casual observer this species would appear to be one of 

 the varieties of Manas termo of § 1 ; and I must confess that, 

 under an amplification of only five hundred diameters, the 

 mistake would be easily made, unless one had become perfectly 

 familiar with the two by prolonged study with a much higher 

 magnifying-power. There is, though, a physiological differ- 

 ence which can be observed when all others could scarcely be 

 noted, which is this : the rate of the systole of the contractile 

 vesicle {cv) of this species is double that oi Monas termo. Like 

 the latter it enjoys two diverse conditions of life — namely, a 

 fixed (figs. 5, b^, 6) and a free (fig. 5'^) state, — frequents the same 

 habitat, progresses with the same means and mode of loco- 

 motion, and obtains its food by similar prehensile organs, and 

 swallows it in the same manner. 



The form of the body is that of an oval, but terminates an- 

 teriorly in an obliquely truncate front ; or, rather, one side of 

 the front projects in the form of a low, rounded prominence, 

 which constitutes the lip [Ij))- The posterior end is either 

 broadly rounded or very bluntly pointed Avhere the pedicel {lyd) 

 is attached. The colour is either greyish or there is none at all. 



