90 THE ROTIFEEA. 



SP. CH. Cluster spherical, consisting of many adults and their young ; tubes so 

 compressed together as to be indistinguishable from each other ; ventral antennae on the 

 corona, between the buccal orifice and the ventral gap, adnate at the base. 



No microscopic object is more beautiful than this lovely globe of living creatures, 

 each bearing its flashing crown of cilia, its ruby eyes and orange-tinted jaws. Fortu- 

 nately it is as common as it is beautiful, and is equally at home in the Swiss Lakes, 

 in the Scotch Lochs, and in the pools of Hampstead Heath. 



The animals all radiate from a common centre (fig. 80), the extremities of their 

 feet being close together, though not in actual contact. The action of their ciliary 

 wreaths imparts a slow motion to the globe, which rolls along, rising and falling, and 

 often returning on its course, in a very aimless fashion. The globe is formed by the co- 

 operation of its inmates, each contributing its secretion to the structure. The newly- 

 hatched free-swimming young may be seen circling round each other, with their bodies 

 curved, and the extremities of their feet directed towards a central spot in the group. 

 In this way they will swim off in a swarm, not actually cohering, but keeping all close 

 together. I have not been able to follow the process further ; but, no doubt, all soon 

 begin to form some sort of tube, and their united secretions fix the swarm together, 

 and at last combine them into a small globe, to which fresh additions are constantly 

 made. A young globe increases its size ^Iso, not only by the growth of the original 

 company, but by the addition to it of its newly-hatched young ; which, as they emerge 

 from the egg, squeeze a place for themselves among their elders. 



But the process has its limits. After a time the globe is too thickly packed, and a 

 young swarm starts off as already described. The largest globes often separate into two 

 portions, each of which soon rounds itself into a sphere ; no doubt they are torn apart by 

 the strain on them produced by the opposing action of the ciliary wreaths in opposite 

 hemispheres. 



The internal structure resembles that of Mclicerta, but a few points require notice. 

 The trophi ! are tinted orange-red, and so is the lower end of the buccal funnel, where 

 are the lips which form an entrance to the mastax : these latter resist the action of 

 caustic potash. The stomach appears to be divided into two chambers, which lie sym- 

 metrically on the right and left sides of the body ; while between and below them the 

 intestine is curved abruptly back towards the dorsal surface ; so that its long rectum 

 ends in an unusually highly placed cloaca. 2 Indeed the whole of the viscera are, as it 

 were, tucked high up into the trunk, leaving its lower end empty of all but the longi- 

 tudinal muscles. Six of these run from the head over the trunk, down the broad, trans- 

 parent, spindle-shaped foot. Five or six bands of transverse muscles cross the trunk, 

 at somewhat regular intervals, from the neck to where it joins the foot. This latter is 

 generally drawn up a little into the body, at its junction with it, so as to make there a 

 conspicuous fold in the integument. The vascular system has no contractile vesicle, 3 

 but its function is performed by the cloaca ; which I have often watched dilating and 

 emptying at regular intervals. The lateral canals arise in a plexus on each side of the 

 corona, slope downwards dorsally to a similar plexus in each shoulder, and throw out 

 on their way branches, above and below the nervous ganglion, which appear to run into 

 each other. From each shoulder-plexus the canal is continued, still near the dorsal 



1 Judge Bedwell (loc, cit.) gives a minute, careful, and original account of the structure and action 

 of the trophi. 



2 Mr. Gosse (loc. cit.) described and figured the frecal pellets, which he supposed to be eggs. His 

 account of them is as follows : " Their form is very peculiar ; it appears to be nearly circular, flattened 

 on one side and convex on the other ; there is considerable difference in their size ; they are of a 

 pale-yellow hue, marked with several blackish specks." 



3 Dr. Cohn (loc. cit.) says that each lateral canal ends in a dilated portion or small contractile 

 bladder, which empties itself into the cloaca, and that the two act alternately. The arrangement, 

 however, seemed to me to be that given in the text. I have drawn in PI. VIII. fig. Bi what I saw. The 

 figure shows a lateral canal (Ic) ending in what I supposed to be the cloaca (cl), and which dilated and 

 contracted regularly. Unfortunately,! have not been able to procure a 'specimen of C. volvox since I 

 read Dr. Cohn's paper. 



