INFUSORIANS. 



567 



colonies growing on Conferva in stagnant water. When the animal is disturbed, the 

 heads droop down towards the stalks. One of the forms most frequently met with 

 is Carchesium, whose tiny branched tree-like colonies resemble moulds ; but a few 

 moments' inspection will undeceive the observer, for the little white globular stalked 

 heads will be seen to be drawn down towards the base of the colony with a rapid 

 jerking movement. 



The trumpet-animalcule (Stentor) is of comparatively large size, being about 

 one-twenty-lifth of an inch in length when extended. It is usually to be found 

 fixed by its pointed end on 

 the under side of duckweed 

 Its form continually alters 

 from a small knob when 

 contracted, to a trumpet - 

 shaped body when extended ; 

 and when in motion its shape 

 continually changes, being in 

 turn ovoid, pyriform, or even 

 spherical. The surface is 

 corrugated and covered with 

 rows of cilia, by means of 

 which the animal swims 

 about. The long cilia at 

 the upper part form a spiral, 

 within the upper margin of 

 which lies the mouth -slit. 

 The mouth opens into a 

 funnel, leading into the sar- 

 code of the interior. The 

 contractile vacuole lies to 

 the right of the mouth-slit, 

 and the nucleus forms an 

 elongated beaded band along 

 the length of the body. The 

 ridge of cilia passing down 

 vertically is the mouth- 

 fringe of a new animalcule 

 about to be formed by division. A cleft sinks in obliquely at one side of the ridge 

 which assumes a wavy outline and later a spiral ; the cleft sinks, till two complete 

 animalcules are formed, with one-half of the nucleus, and a contractile vacuole in 

 each. New individuals may also arise by the budding off of tiny ciliated embryos 

 from the nucleus. The species of trumpet-animalcule most commonly met with is 

 of a brilliant green colour ; frequently clusters of them are found clinging by their 

 pointed ends to the stem of a water-weed. A specimen has been cut into three 

 parts, care being taken to leave a fragment of nucleus in each, with the result 

 that each part has repaired itself into a complete animal; the central part, for 

 instance, developing a head and a tail-end. 



MARINE ANIMALCULE, Acincta (magnified 600 diameters). 



