47 



siderable, decreasing a liftle in the gemmuh-stage. The niimher 

 of the green stages of divisioti is comparatively great^ hut in gem- 

 muJes theg are absent; hardlg the gemmules have germinated, 

 however, and the number increases again. The number of the coloiir- 

 less algae irith structure is small and remains rather constant 

 during development^ showing a considerable decrease diiring and 

 after the gemmule stage. The number of the colourless ones ivithout 

 structure is not great at the beginning, but increases rather con- 

 siderahhj afterwards, also showing a strong decrease (as far as 

 we mag judge) during or after the gemmule stage. 



3. Li the course of the development of the tissues of colourless 

 Sponglllae the number of the green algae remains constantly smdll, 

 in order to disappear completely in the gemmule stage; ivhen, 

 however, the gemmules have germinated the number immediatelg 

 increases. The number of the green stages of division is constantly 

 very small; as a t'ule they are even missing. The number of the 

 colourless algae with structure is not great and remaijis rather 

 constant during development, showing a considerable decrease during 

 and after the gemmule stage. The numher of the colourless ones 

 tmthout structure is ratJier great at the beginning and increases 

 considerably afterwards, also showing a great decrease during and 

 after the gemmide stage. 



4. In this way one observes in the tissues of the green Spon- 

 gillae as well as in those of the colourless ones a gradual change 

 of number of the various stages of algae: from very young tissue to 

 full-grown, from full-grown tissue to gemmules, and from gemmules 

 to very young tissue again. 



5. During or immediatelg after the gemmule-stage the tissue of 

 a Spongilla contains a minimum of green and colourless algae. 



6. ]n the green sponges the numher of the green algae is 

 usually much greater than that of the colourless ones (with, and 

 without structure) together ; only in some cases this number is equal. 



7. In the colourless sponges the nutnber of the green algae is 

 always much smaller than that of the colourless ones together. 



8. In the green sponges the green algae are always much more 

 tiumerous than in the colourless sponges. 



