16 Mr. H. J. Carter on the Circulation of the 



a similar way, and either germinate after having become sta- 

 tionary, or pass after a short time into dissolution, as the sacs 

 have hitherto done which I have just described. 



I had forgotten also to mention, that there is frequently a 

 considerable space between the outer and inner spherical cell 

 just described ; and here, before the green mass has undergone 

 division, may frequently be seen one or more of the common- 

 sized gonidia, under their ciliated active form ; which, after the 

 division has taken place, passes into the diffluent one, when they 

 may be seen, on the contrary, creeping slowly over the inner 

 surface of the external spherical cell, in a polymorphic state. 



The tenacity to life of the green matter and mucus-layer 

 after the death of the cell-wall is so great in the species of 

 Zygnema, to which I shall have occasion to allude presently, 

 that although all the filaments broke down from the destruction 

 and dissolution of the cell-wall a few days after they had been 

 placed in a basin of water for examination, the mucus-layer 

 continued to hold the spiral bands together, with but little 

 alteration, except in form and position, for three weeks after- 

 wards, when the whole began to break up into small parcels of 

 green matter, of variable sizes, below the 700th part of an inch 

 in diameter, each of which is now rounded with a mucus-in- 

 vestment that is carrying them about under the form of Actin- 

 ophrys Sol; but with a halo of short cilia in many, immediately 

 round the circumference, in addition to the long radii. Whether 

 they will ultimately germinate, or their contents — now of a 

 bright yellowish-green, but still presenting a tint of brown in 

 it — pass into gonidia, time will show ; but from the brownish 

 tint, I should think the latter the most likely sequence. 



Circulation. 



What is commonly understood by the '^ circulation in the 

 Characese,'^ is, that the cell-contents move round the internode ; 

 but this is a very vague idea of the phsenomenon. There is but 

 one part that moves, viz. the mucus-layer; and another part which 

 is circulated, namely the axial fluid ; while the green layer, so 

 long as it is uninjured, remains stationary. 



The axial fluid, as before stated, is impelled by the uneven 

 surface of the mucus-layer, as may be seen by watching the 

 motion of a bunch of the raphides when struck by one of the 

 mucus-prominences. It will then present not only an accelera- 

 tion of its progress, but, the force having been communicated to 

 the radiated crystals next the mucus-layer, causes it to rotate 

 backwards, or in the contrary direction to that in which it is 

 being transported. Hence, as I have before stated that the 



