360 W. ARCHER. 



— the ectosarc, the contractile vacuoles — there is not much 

 in common with the corresponding portion of the body-mass 

 in the Askeleta. 



Unlike Actinosphserium, where, as is seen, the reverse state 

 of affairs prevails, Hertwig and Lesser point out that in the 

 Skeletophora (including also the forms I have proposed to 

 group as Chlamydophora) the ectosarc, which is permeated by 

 coarser or finer granules, is the portion of the substance 

 into which the nutriment is taken, and in which assimila- 

 tion is effected, the nutritive particles never reaching the 

 central part.- This latter appears to be, therefore, of a finely 

 granular or homogeneous nature, of pale greyish-blue tint, 

 a more or less marked line of demarcation often evident, but 

 this not due to any special membrane mutually limiting off the 

 two regions. , 



But that in all the skeleton-bearing Heliozoa the structure 

 is to be interpreted as Hertwig and Lesser thus lay down is, 

 I fancy, not to be regarded as decided. To my eyes, as yet, 

 the body-mass from the nucleus outwards to the bases of 

 the pseudopodia does not always show any very sharply 

 marked differentiation of consistence (though, on the other 

 hand, Acanthocystis sp'inifera, for instance, does so) ; whilst 

 the fact that the incepted food does not occupy the centre 

 of the body-mass may be due to the hindrance afforded by 

 the subcentral, rigid, sometimes comparatively large, nu- 

 cleus. There are some species, indeed, in the substance of 

 which crude food of any kind (diatoms or the like) is rarely, and 

 in others I fancy one might almost say is never, to be noticed. 



As regards the pseudopodia, the Heliozoa Skeletophora, 

 just like the Monothalamia, present various species in which, 

 as may be seen, these characteristically appear granular or 

 homogeneous, branched or unbranched ; anastomosis of neigh- 

 bouring pseudopodia sometimes, but not often occurs. The 

 pseudopodia of some forms, according to Grenacher^ and 

 Greeff,^ present a slender axis (like Actinosphaerium) of the 

 greatest delicacy. 



In the different species the granular or non-granular na- 

 ture, as well as the comparative thickness (one might 

 better say the thinness) of the pseudopodia seems to me 

 to be a very constant characteristic, whilst quite as much 

 so is also the average or the extreme relative length of which 

 they are capable in the various forms. Of course this re- 

 mark applies to examples in a normal and undisturbed state 



' " Benierkungen iiber Acanthocystis viridis " in ' Zeitsclir. fiir wiss. 

 Zool./Bd.xix, p. 292. 

 2 'Archiv. fiir Mikrosk. Anat./ Bd. v, p. 4S4. 



