OF THE ROTATORIA. 449 



spheroidal or tentacular particles are arranged in a ring round the middle of 

 the body, and appear to have some internal connexion with the thin mem- 

 branous cylinder. At first, new additions are made to both extremities of 

 the enlarging ling ; but the jerking contractions of the animal at length force 

 the caudal end of the cylinder down upon the leaf, to which it becomes se- 

 cui-ely cemented by the same viscous secretion as causes the little spheres to 

 cohere. All the new additions are now made to the free extremity, which, 

 as Ehrenberg remarks, never extends beyond the level of the cloacal aper- 

 ture of the outstretched animal. In the new-born being, therefore, the parts, 

 as in the adult, are all present ; they only require to be expanded by the 

 ordinary process of growth." 



Mr. Gosse's account of a newly-hatched Melicerta implies a greater aber- 

 ration of form than that narrated by Prof. Wilhamson. He states that 

 " its form is trumpet- shaped like that of Stentor, with a wreath of cilia 

 aroimd the head, internipted at two oj^posite points. The central portion of 

 the head rises into a low cone." After various movements and gp^ations for 

 an hoiu', the young animal settled itself, and the form of the adult became 

 manifest : " the four petals of the disk were well made out, though the sinu- 

 osities were yet shallow ; the antennae at first were only small square nipples, 

 but soon shot out into the usual form ; the ciliated chin was distinct, as was 

 also the whirling of the pellet-cup immediately beneath it." 



We are indebted to Mr. Huxley for an elaborate description of the young 

 of Lacinularia sociaUs (XXXYII. 10, 11). ^' The youngest foetuses," he 

 writes, " are about T^j-th of an inch in length. The head is abruptly trun- 

 cated, and separated by a constriction from the body ; a sudden narrowing 

 separates the other extremity of the body from the peduncle, which is ex- 

 ceedingly short and provided with a ciliated cavity, a sort of sucker, at its 

 extremity. The head is nearly cii'cular seen from above, and presents a central 

 protuberance, in which the two eye-spots are situated. The margins of this 

 protuberance are provided mth long cilia ; it will become the upper circlet 

 of cilia in the adult. The margin of the head projects beyond this, and is 

 fringed with a circlet of shorter cilia in the adult. The internal organs are 

 perceived with chfficulty ; but the three divisions of the alimentary canal, 

 which is as yet straight and terminates in a transparent cloaca, may be 

 readily made out. The water-vascular canals cannot be seen ; but their pre- 

 sence is indicated by the movement of their contained cilia here and there. 



'" In young Lacinidarice ^ih of an inch in length, the head has become 

 triangular ; the peduncle is much elongated, and it gradually takes on the 

 perfect form. The young had pre\iously crept about in the gelatinous in- 

 vestment of the parents; they now begin to "swarm," uniting together by 

 their caudal extremities, and are readily pressed out as united, free, swim- 

 ming colonies, resembling in this state the genus Conochilas.''' 



Mr. Brightwell gives the appended brief account of the BmcMonus Baheri 

 on its escape from the egg : — '-At first it had the appearance of an oblong 

 ball ; by degrees the anterior part spread, and the wheel processes were de- 

 veloped. Soon after, the posterior shell (lorica) processes were visible in a 

 semilunar shape, with the points nearly touching each other, which gradually 

 expanded." 



These examples are sufficient to illustrate the general character of embryo 

 Rotatoria and their progressive assumption of the adult form ; they more- 

 over furnish evidence of the doctrine that there is no metamorphosis, or 

 transformation, in the proper sense of the word — no change but what is expli- 

 cable by the ordinary laws of growth, or progressive expansion or evolution. 

 Ehrenberg has announced it as a fact {Monatsh. d. Berl. Alrid. 1853, p. 532), 



