THE FORAMINIFERA 



69 



In a short time the protoplasm which lies outside the aperture 

 of each of the spheres secretes the wall of a second chamber of 

 characteristic form, and the young individual is then clearly 

 recognisable in size and shape as the two-chambered young of the 

 megalospheric form (Fig. 11, b). 



The nature of the parent which gives rise to this brood of 

 megalospheric young is determined by decalcifying specimens 

 which are entering on the reproductive phase, before the proto- 

 plasm has left the central chambers. In upwards of fifty cases 



m-.c. 



FIG 11 



Young megalospheric individuals of Polystomella crispa. a, a group of six, two days after their 

 formation. Four chambers are formed. 6, a specimen with two chambers, decalcified and 

 stained ; N, the nucleus ; n, irregular stained mass, c, a specimen with nine chambers, simi- 

 larly treated ; N and n as in 6 ; sp.c, spiral canal of the canal system ; in this specimen it 

 becomes irregular near the last-formed chamber; m.c, meridional canal. 



thus examined the centre was found to be occupied by a micro- 

 sphere. We have then, in this process, a transition from the 

 microspheric to the megalospheric form. 



Schaudinn (44, p. 94), has found great variation in the size of 

 the megalospheres produced by one parent, namely, from 10 to 120 /u. 

 He therefore holds that the two forms of Polystomella, though differing 

 in their nuclear characters, are not always distinguishable by the size of 

 the central chambers. He also finds (p. 93) that in some cases the shell 

 of the young megalospheric form is not secreted until the spherical masses 

 of protoplasm have wandered about for a long time. 



The details of the reproductive process given above are those which I 

 have invariably observed in specimens which were kept in clean sea-water. 



