240 EVENINGS AT THE MICROSCOPE. 



distance within the aperture of the lorica. This articula- 

 tion is formed by an infolding of the skin, but is perma- 

 nent in its position. 



The most remarkable circumstance connected with this 

 elegant little animal is the unusual form of the dental 

 apparatus, which differs so immensely from that of Bra- 

 chionus, that we should never recognise it as consisting of 

 the same organs, if we had not numerous intermediate links, 

 which by insensible gradations connect the two remote 

 forms. 



The mastax is a somewhat slender sac, much produced 

 in length, and with the component lobes greatly and irre- 

 gularly developed. The incus has a fulcrum of great 

 length and slenderness, a straight rod with a dilated foot. 

 The rami are small, and pincer- shaped, but with the 

 angles greatly produced. The mallei have long, slender, 

 incurved manubria and simple unci. 



But the remarkable circumstance is the unsymmetrical 

 character of the apparatus. The left side is much more 

 developed than the right. The left angle of the incus 

 descends to a greater distance than the right ; and its 

 extremity is spread out into a surface with several irre- 

 gular points, to which muscular threads are attached. The 

 ramus also of the same side is larger than its fellow ; so 

 with the mallei. The manubrium of the right is compara- 

 tively short, very slender, and of uniform thickness ; with 

 a long, slender, rod-like uncus, doubly bent in the middle. 

 The left is much longer, irregularly swollen, clubbed at the 

 articulation, and bearing a thick, curved, knotted uncus, 

 which terminates at a point not precisely opposite the tip 

 of its fellow. These circumstances, combined with the 

 unsymmetrical character of the dorsal ridge, of the foot- 

 spine, and of some other organs, render this genus a 

 highly curious one to the naturalist. 



The little Whiptail is as lively in its motions as it is 

 elegant in its form. When swimming, it glides with con- 



