32 OF THE RHIZOPODA IN GENERAL:— RETICULARIA. 



size. But in the Operculine the diameter of the pores is so much smaller, — being commonly 

 no more than 1-1 0,000th of an inch, and often less, — that only the very finest pseudopodian 

 threads can issue from them, and only the minutest granules can be received into them. 

 Certain facts in the structure of the shell, to be hereafter detailed (Chap. II), render it almost 

 certain that the protoplasmic substance extends itself at certain times, if not constantly, over 

 the whole exterior of the shell, as in Gromia (^ 33) ; and hence it is by no means impossible 

 that the digestive process may really be performed in this external layer, so that only the 

 products of digestion may have to pass into the portion of the sarcode-body occupying the 

 cavity of the shell. 



37. The sarcode-body of such Foramini/era as have been observed in the living state, is 

 observed to be more or less deeply coloured ; its tint being in some instances a yellowish- 

 brown, in other cases a crimson-red. This colour seems in some instances to be uniformly 

 diffused through the whole mass of the sarcode, probably owing to the fine state of division 

 of the particles which possess it ; but in the larger forms it occurs in much larger and more 

 scattered masses, which appear sometimes to be collections of granules, and in other 

 cases to be vacuoles filled with a coloured liquid. In the polythalamous Foramini/era it is 

 nearly always to be observed that the colour is deepest in the segments of the body which 

 occupy the oldest chambers, and that it fades progressively in the segments which intervene 

 between these and the one that occupies the last-formed chamber, which is often nearly colour- 

 less. There is strong reason to believe that the colouring material is directly derived from 

 external sources, thougli modified in some cases by the agency of tlie animal itself. It was 

 found by Schultze, that he could increase the intensity of the colour, and cause even the 

 last-formed segment to be dyed with it, by feeding the animals with substances fitted to 

 impart it ; whilst, on the other hand, by depriving them of food that would furnish colour, 

 he could reduce the older segments to almost the same state of deficiency in this respect as is 

 usually presented by the last segment alone. It is stated by Schultze that the colouring 

 matter of Foramini/era, when treated with dilute sulphuric or hydrochloric acid, is changed 

 to an intense verdigris green ; and by dilute nitric acid, first to green and then to yellow. 

 Concentrated sulphuric acid destroys the colouring substance, but when combined with sugar 

 renders it green. By concentrated solutions of potass and soda, the coloured granules are 

 dissipated without change ; and in ether and alcohol they are readily and completely 

 dissolved. In these reactions the colouring matter agrees with that of the Dialomacece, from 

 which tribe the greatest part of the food of the Foramini/era is probably derived. 



REPRODUCTION OF RIIIZOPODA. 



38. So little is at present known of the manner in which Rhizopods belonging to any of 

 the foregoing types propagate their kind, that it seems preferable to bring together 

 the principal facts hitherto recorded respecting the mode of reproduction in all these 

 groups ; more especially as they will be found to bear a very close resemblance to one 

 another. 



39. The deficiency of structural differentiation, either morphological or histological, which 



