518 THE NATURAL HISTORY OF 



colour, or of one inclining to blood red or green, with a 

 central, multiform, red nucleus; seldom altogether green. 

 The mucous envelope is frequently wanting, or is so 

 closely applied to the cell as to be scarcely apparent. 

 The red nucleus appears to have a special coat, which, 

 however, probably does not exist ; it appears as a hollow 

 vesicle, placed on or near to the inner surface of the 

 wall, and presents on one side an opening, or, only 

 half or two thirds of it may exist. The nucleus is de- 

 tached by pressure, and in the spot where it was situated 

 appears a colourless vacuity. The anterior extremity of 

 the mother-cell exhibits either none, or cobweb-like pro- 

 cesses, which are but seldom apparent, particularly in the 

 globular or ellipsoidal forms which represent H.pluv. 

 rotundatus. Or there exists, at the anterior extremity, a 

 wart-like transparent process, from which arise simple or 

 bifurcate, filamentous elongations or tentacles, as in the 

 form H. pluv. papillatus. When this process is conical 

 and attenuated we have H. pluv. rostellatus. Not un- 

 frequently short setose hairs spring from the periphery 

 of the mother-cell, stretching across the space between 

 this and the mucous envelope, and which characterise 

 H. pluv. setiger. 



These motile forms, which may be comprehended 

 under the common name of H. pluv. versatilis, are trans- 

 formed into the still form, becoming round, and retracting 

 the various processes above noticed ; whilst the mucous 

 envelope is condensed into a papyracous membrane. 



This still Hcematococcus pluvialis, quiescens, aquaticus, 

 genuinus, from O0001 to 0'0029 Paris inch in diameter, 

 forms loose masses without its being retained, however, by 

 any special mucous hypothallus. It sometimes has, and 

 sometimes has not a mucous envelope ; the mother-cell is 

 either entirely filled by the sometimes grumose-granular, 

 sometimes grumose, or even gelatinous contents, so that 

 the boundary line is reduced to capillary thickness or is 

 completely obliterated ; or it is only partially filled, and the 

 contents then form a smaller and, most usually, central 



