154 



the canals, which lodges the big carmine grains, does belong to 

 amoeboid cells. Perhaps one is now inclined to look upon these 

 as being pinacocytes, because in general the canals are supposed 

 to be lined by this sort of cells — see eg. Delage 14. But, 

 probably, the latter is not right for Spongillidae ; a fact which 

 "Weltner (67) pointed out already, and which I too could state. 

 I namely found the canals lined : here by flat pinacocytes , 

 there by amoebocytes with symbiotic algae, yonder again by 

 apparently undiff'erentiated plasmic substance (Fig. 71). (Or must 

 one, in both last cases, imagine the pinacocytes to be present, 

 but extended so thin that they escape to our sight?) As the 

 pinacocytes, moreover, generally do not show such an irregular shape 

 (as the carmine-carrying cells in the above mentioned macerated 

 material) and as they usually are also easily to be recognized 

 as cells in a living preparation (while here we are speaking of 

 apparently undifferentiated plasma), one had better explain this 

 plasma, these amoeboid cells, as belonging to the parenchyma, 

 which then is not lined here by pinacocytes — or by very thin, 

 not separately visible pinacocytes? — . I will return to this sub- 

 ject in the Appendix. 



At any rate the mentioned apparently undifferentiated plasma 

 belongs to amoeboid cells. But, as said, one may not yet con- 

 clude from this, that the flowing plasmic layer at the exterior 

 of the flagellated chambers also belongs to amoeboid cells. If, 

 however, this was in fact the case, we could ascribe several 

 morphological meanings to those cells. In the first place one would 

 be inclined to look upon this layer as being pinacocytes again 

 or better parenchyma lined with thin pinacocytes — as Delage 

 (14) gives — or parenchyma without pinacocytes. On the other 

 side, however, one might say that here we had amoeboid cells, 

 which probably entirely surround the prosopyles of the chambers, 

 in other words, something as the well known porocytes of cal- 

 careous sponges. I will also return to this question in the 

 Appendix. 



For the rest, the whole question of the morphological meaning 

 of the apparently undifferentiated plasma of the canal walls only 



