170 Phenomena of the Poclura Test. 



the water in which these incidents were first traced, one or more of 

 which invariably fell victims to each Actinophryan, and in their 

 metabolic efi'orts to escape, until they finally sank engulfed, pre- 

 sented a singularly interesting spectacle. This stationary condition 

 is maintained for a longer or shorter time, the pseudopoda are then 

 withdrawn, the former shapes resumed, and the onward vibratory 

 movements renewed. I may add that they show a tendency to 

 aggregate, and are mostly limited to a small portion of the field. 



The question here arises, are we to regard these little organisms 

 as independent forms, or as phases — and advanced ones — of Actino- 

 phryan life ? I incline to the latter view ; for may we not 

 reasonably expect that, equally with creatures of a higher type of 

 organization, the humble Adlnoplirys will fulfil those universal 

 laws of nature which dictate that, no matter how frequent the pro- 

 pagation by self-division — no matter how numerous the partheno- 

 genic descents — every living organism must sooner or later revert 

 to the congress of two individuals, to secure the perpetuity of race 

 by means of the fecundated germ, and that the fixed or feebly 

 locomotive forms of animal life shall find in their actively motile 

 embryonic developments the mode of efi'ecting their dispersion in 

 space. 



VI. — On the various Phenomena exhibited ly the Poclura Test 

 under ordinary and extraordinary MicroseopiG Resolving 

 Powers. By G. W. Royston-Pigott, M.A., M.D,, F.C.P.S., 

 Cantab., late Fellow of St. Peter's College, M.R.C.P., F.R.A.S., 

 M.R.I., F.R.M.S. 



The variety and subtlety of this queen of test-objects under various 

 treatment of illumination and magnified imagery strike the eye of 

 every observer with astonishment, who examines the phenomena 

 presented under different conditions of illumination, and difi'erent 

 adjustments in the objectives and eye-pieces, and greater or less 

 penetration or depth of focal vision. The microscopist with whom 

 this precious, I would almost say, peerless object has been a prime 

 favourite, possesses within it a complete Thesaurus of signs by which 

 he can pronounce upon the performance of his glasses. In this 

 very wealth of optical efiects lies its chief value and interest. So 

 long indeed as the object was made to show itself in one " standard " 

 form, as the ne plus ultra of microscopy, and so long as both 

 makers and purchasers of glasses conjointly decreed the standard 

 test, and forbade, under penalty of contempt and ridicule, any other 

 view, further advance appeared unnecessary. 



