GENUS GEOMIA.— GEOMIA TEEEICOLA. 279 



large, clear or pale granular nucleus situated centrally or eccentrically, and 

 also variable proportions of vacuoles, usually lew and of different sizes. 

 A vacuole was at times observed to gradually disappear; and at times one 

 or more were seen to make their appearance; but it was doubtful whether 

 any of these exactly corresponded with the contractile vesicle of other 

 rhizopods. 



Professor Schulze intimates the absence of a contractile vesicle in 

 Gromia ;* but Dr. Wallich remarks that in one instance he detected this 

 temporary organ in Gromia oviformis.-f 



The food contents observed in Gromia terricola consisted of minute 

 diatoms, fragments of Lyngbya, and globular, green algse, together with 

 sand and other materials. 



In the emission of the pseudopodal filaments of Gromia terricola, the 

 protoplasm pours from the mouth of the shell in a slow manner, and grad- 

 ually envelopes the body, as represented in figs. 1-3. From the protoplas- 

 mic envelope delicate streams extend outwardly, at first emanating from the 

 front ; they more or less rapidly multiply and radiate in all directions. 

 Gradually extending, they fork into branches of the utmost tenuity. Con- 

 tiguous branches freely join or anastomose with one another, and thus 

 establish an intricate net, which in its full extent covers an area upward 

 of four times the diameter of that of the body of the Gromia. The pseu- 

 dopodal net incessantly changes, — putting forth new branches in any posi- 

 tion, while others are withdrawn, — diminishing and disappearing in one 

 spot, while it spreads and becomes more complex in another spot. 



Gromia terricola, with its pseudopodal net fully spread, like its near 

 relatives, reminds one of a spider occupying the centre of a circular web. 

 If we imagine every thread of the latter to be a living extension of the 

 animal under the same control as its limbs, the spider would be a nearer 

 likeness to the Gromia Over each and every thread of the pseudopodal 

 net Gromia has as complete control as if the threads were permanently 

 differentiated limbs acted on by particular muscles, and directed in their 

 movements by nervous agency. Threads dissolve their connection and are 

 withdrawn ; new ones are formed and establish other connections : they 

 bend; the) 7 contract into a spiral; they occasionally move like the lashing 

 of a whip, and indeed produce almost every conceivable variety of 



*Arehiv f. mikros. Anatomic-, 187.">, 116. 



tAnuals and Magazine of Natural History, 1863, 458. 



