594 ORDER HETEROTRICHA. 



the fine ciliary clothing of the general surface of the integument occasionally 

 supplemented with a few long, fine sets, which are not, however, so con- 

 spicuously developed as in the two preceding species j endoplast trans- 

 parent, moniliform. Length 1-192" to 1-96". 



Hab. — Fresh water, on aquatic plants ; social. 



As previously related,* the pigmentary substance distributed throughout the 

 cortex that communicates to this species its characteristic cerulean hue has been 

 submitted by Prof. E. Ray Lankester to spectroscopic analysis with highly inter- 

 esting results. Two absorption bands of remarkable intensity were clearly e.xhibited 

 whether e.xamples were examined either singly or en masse, these difiering so 

 essentially from the bands yielded by all other organic substances that this investigator 

 has conferred upon it the distinctive title of " Stentorin." Velella, an organism which 

 from its relatively low position in the zoological scale might have been expected to 

 yield a closely corresponding spectrum, was found on similar submission to the 

 micro-spectroscope to produce no band or bands of absorption whatever. The 

 spectroscopic examination of the Stentors in quantity was greatly facilitated by the 

 presence in the aquarium that contained them of numbers of the annelid Chceto- 

 gaster diaphanus, many of which had gorged themselves with the infusoria, thus 

 proving convenient collectors of the material required. 



Stentor igneus, Ehr. Pl. XXX. Figs. 1-4. 



Body of moderate size, changeable in shape to a very limited extent ; 

 the width of the peristome, when most fully extended, equal to about one-half 

 of the entire length ; internal parenchyma coloured bright green through the 

 presence of a rich layer of chlorophyll-granules ; the more transparent 

 superficial layer containing in addition finely granular pigment of an intense 

 scarlet hue, this being usually most abundant in the neighbourhood 

 of the peristome ; endoplast ovate or spherical. Length of extended body 

 1-72". 



Hab. — Pond water, on Hottonia, Ranunculus, and other water plants ; 

 social. 



The author obtained this species, in IVIay 1876, in considerable abundance 

 attached to the leaves of the water crowfoot, Rafiuttadus aquatilis, taken from 

 a small pond on Wandsworth Common. On many occasions it was noted that the 

 breadth of the extended peristome in this short, trumpet-shaped animalcule con- 

 siderably exceeds that given by Stein, it in some instances being equal to that of its 

 entire height. The rich colouring of this form renders it perhaps one of the most 

 attractive and ornamental representatives of its genus, more especially as exhibited 

 with the aid of the parabolic condenser, when every tint is thrown up on the dark 

 background with intensified distinctness. On one occasion, in connection with the 

 death and disintegration of an adult example, the release was observ'ed from its debris 

 of a spheroidal embryo, possessing an anterior crescent-shaped row of larger adoral 

 cilia and a general covering of finer ones, the germ in its entirety thus agreeing 

 essentially with those already described by Claparfede and Lachmann in relationship 

 with Stentor Reeselii. 



Stentor niger, Ehr. 



Body of moderate size, exceedingly changeable in shape, when fully 

 extended nearly three tiines as long as broad, the surface parenchyma 



* Vol. I. p. 79. 



