Boyal Microscopical Society. 71 



But during tlie whole time occupied in this resting condition, there 

 was no change of any kind that could be detected by the highest 

 powers we could employ. We have drawn a form in this condition 

 at Fig. 12. Now we were several times perplexed by tlie sudden 

 disappearance of these " disks " from positions in the field accurately 

 marked, so that we might constantly and easily return to them. 

 Was it that they resumed activity and swam away ? We could only 

 reply by watching them to the end. This was done, and Fig. 13, 

 PI. LII., gives a feeble idea of the result. The disk or sphere 

 opened slowly, and there was poured out in continually increasing 

 volume a glairy-looking fluid. It was not difficult to distinguish it 

 from the fluid into which it was poured ; the optical efiect was like 

 that produced by the pouring of strong spirit into water. But we 

 could discover no granules in it. We exhausted every means at our 

 disposal, and employed the highest magnification, but without result. 

 Certainly nothing like the sporules we had seen before could be 

 detected here. But we determined, after seeing this the second 

 time, to make the field in which the outflow occurred the subject of 

 special and continuous research. It was a comparatively clear field, 

 and somewhat within the ring which most of these monads make 

 around the covering glass when retained alive for any length of 

 time.* We employed powers of from 2500 to 5000 diameters, and 

 Fig. 14, PI. LI., upper portion, represents a portion of the field the 

 seventh hour after emission, but the tiny dots drawn there are at fault 

 in presenting them as opaque objects, whereas they were semi-trans- ' 

 parent, and of a yellowish hue. They were thus distinguished from 

 the sporules we had seen at their emission, for they were dark and 

 opaque. They came into view suddenly. A place where we could by 

 no means employed see one, would all at once reveal one. After this 

 their growth was comparatively rapid. Fig. 15 represents a portion 

 of the same field as Fig. 14, drawn an hour and ten minutes after 

 that in Fig. 14. Fig. 16 depicts another portion of the field drawn 

 at the expiration of two hours more. From this time the growth 

 was very rapid. The sharp-pointed bodies in Fig. 16 began to 

 assume a rounder form, and the pointed end always became the end 

 from which the flagellum developed. Fig. 17 was drawn at the 

 expiration of another ninety minutes, when motion first showed 

 itself ; this, however, was not the motion usual to the monad, but a 

 motion of horizontal vibration from a through h and c to tZ in 

 Fig. 17, and then back again; after which it swam away, and 

 rapidly became plump as in Fig. 18, and then was followed into 

 the stages drawn from Figs. 2 to 9, PI. LII., thus completing the 

 cycle of its developmental history. 



We have strong negative evidence that the larger forms which 

 unite with the common ones (Fig. 10, PI. LII.) are not subject 



* 'Micros. Jouinal,' January, 187i, p. 8. 



