236 SUMMARY OF CURRENT RESEARCHES RELATING TO 



lopment of the carapace in certain regions. A new genus Distyla 

 is defined as having the carapace depressed, open anteriorly and 

 closed behind ; the foot is one-jointed and has two long " toes." The 

 carapace is ridged in the region of the foot, the wheel-organ is feebly 

 developed. D. gissensis and D. ludwigii are the new species. 



In Euchlanis dilatata the central organ of the nervous system 

 consists of a number of lobes, and carries one large red eye ; it is 

 connected by fine filaments with a pit of tactile function. At the 

 hinder end of the body there are two organs, which appear to be the 

 chief ganglia of the nervous system, for they are long and spindle- 

 shaped, and pass anteriorly and posteriorly into fine filaments. 

 Squamella bractea has four eyes, of which the anterior are somewhat 

 larger than the hinder pair, and distinctly contain a refractive body. 

 Behind there is a small tactile tube, which is beset at its end with 

 setfe. In Pterodina the foot has not, as in other Eotifers, the function 

 of an attaching organ, but serves as the hind-gut ( ? ) ; it can be con- 

 tracted, but not retracted. 



In the second half of this essay Eckstein enters into a general 

 biological, anatomical, and developmental history of the Eotatoria. 

 He finds that there is no true segmentation of the body, and that the 

 jointing of the integument is dependent on the firmness of this layer. 

 The apparent, or rather externally radial form of some (StepJianoceros, 

 Floscularia) is due to their fixed mode of life. 



A short comparative account of the wheel-organ is given. The 

 colourless muscles are (1) quite homogeneous, each being formed of a 

 single fine fibre, or (2) have in their centre a chain-of-pearl-like band 

 of clear nuclei, or (3) they are distinctly transversely striated. Whore, 

 as in Scaridium, there is great muscular activity, all the muscles of the 

 body are striated. There appears to be still much to learn with regard 

 to the nervous system, Leydig, for example, refusing to recognize a 

 central organ in Lacinularia, and describing, as chief ganglia, the four 

 nucleated spindle-shaped swellings which lie by the mastax and the 

 rectum. The eye-spots may lie on, behind, or in front of the central 

 ganglion ; a convex transparent lens is present in some, though not in 

 all ; the eyes may be paired or unpaired, or two may be fused into 

 one. Other red spots, without refractive bodies connected with them, 

 are sometimes found on the wheel-organ. The organ taken by Huxley 

 for an otocyst is rather the calcareous pouch, which is an appendage 

 to the ganglion, and lies either in front of or behind it. It has a 

 spherical or reniform shape, and consists in some cases of irregular 

 aggregations of calcareous granules ; it is often continued forwards 

 as a fine granular cord, or as a broad sac-like organ, attached at one 

 end, and by the other projecting freely into the coelom ; further ob- 

 servations are necessary to determine the function of this apparatus. 



In all Rotatoria (pace Huxley) the anus lies on the neural side ; 

 the excretory system has a contractile vesicle formed of a fine struc- 

 tureless membrane, bounded by a system of delicate and almost 

 invisible muscular fibres, which suddenly contract its lumen ; the 

 vesicle enlarges again slowly by the elasticity of its walls, or by the 

 pressure of the inflowing fluid. The canal on either side may be 



