422 GENERAL HISTORY OF THE INFUSORIA. 



and swam about as lively and apparently uninjured as ever. In one I saw 

 several specimens of a long slender Fragilaria hose in the cavity of the body, 

 and in the stomach of another the long cell of a Conferva." 



From the manner in which the food is obtained, apparently without any 

 selection on the part of the animals, the vortex driving into the mouth what- 

 ever particles may come within its reach, we might conclude that the con- 

 tents of the stomach must be of a very miscellaneous character. This is true 

 to a great extent ; yet the Rotifers can eject what is unsuitable, and they 

 have the power of moving from place to place in search of suitable nutri- 

 ment, or at least, as in the fixed forms, of arresting and withdi^a^ving the 

 ciliary apparatus until noxious materials are floated past, or appropriate ones 

 have come vrithin reach. That they are passive recipients of the cuiTent 

 setting into their mouths, is indicated by their swallowing carmine or other 

 colouring matters mixed with the water, which, as Mr. Gosse observes, are 

 deleterious to them. 



The feeding of Rotatoria with colouring matter serves a practical purpose 

 in the examination of their structure ; for it helps to reveal, by the contrast 

 of coloured with uncoloured parts, details of structure not apparent amid the 

 uniform and dehcate hue of the entire organism in its natural state. For 

 example, Mr. Gosse writes — " The process of swallowing carmine enabled 

 me to see (in Melicerta), very distinctly, that the oesophagus enters the giz- 

 zard between the larger ends of the jaw-mullers, and that the stomach-duct 

 leads off from their smaller ends through the semiglobular lobe beneath." 

 The same observer employed this means to demonstrate the manner in which 

 the case of the AleUcerta is deposited, and with very satisfactory results 

 (see p. 425). 



The Secreting System. — Special organs of secretion exhibit themselves in 

 the Rotatoria under the simplest form of cells, and of involutions of the lining 

 membrane of the alimentary tube, as sacs and tubules. Frequently their 

 contents are coloiu^ed ; and these always differ in density and physical ap- 

 pearance from the general fluids of the body. The glandular organs situated 

 about the walls of the digestive canal, are supposed to have discharging ducts 

 thi'ough which their contents percolate into that tube. 



The testes or spermatic glands in the male, and the ovary in the female — 

 both of them secreting organs, — together with some accessory secerning vesi- 

 cles, will be described under the section on the Reproductive Organs. Some- 

 thing has already been said of some other glands in the last section, on the 

 Digestive Organs : a more precise account is, however, necessary. 



The most constant glands are the two situated on the upper surface of the 

 stomach near the entrance of the gastric or proventricular tube, and some- 

 times on that tube itself (XXXVIII. 2Q h, 271). They are usually hemi- 

 spherical or oval, but assume other shapes, as pyriform, conical, cyhndrical, 

 reniform, crescentic, and forked. In a few, e. g. Noteus and some Brachioncm, 

 they are stalked, or, more properly speaking, have an elongated, tapering ex- 

 tremity. Cylindrical or club-shaped glands are seen in Notommata clavulata, 

 and forked ones in Diglena lamistris. In these two species, and also in 3Ie- 

 galotrocha there are likewise foiu* long filiform tubes, equalling the glands in 

 length, and of the like coloiu% but opening at the centre instead of the fore- 

 part of the stomach. In Polyarthra, Leydig noticed two elongated secreting- 

 sacs attached to the jposterior surface, and in Lacinularia, a pair of glands, 

 instead of a single one, at the fore part of the stomach. J^ot being able 

 to detect the ducts of the ^' 2-3 pyriform glandular (?) -looking bodies often 

 attached to the base of the upper stomach (of Melicerta) near the constriction 

 which separates it from the lower one, Prof. Williamson hesitates to call 



