47 



siderable, decreasing a little i?i the gemmule-stage. The number 

 of the green stages of division is comparatively great, but in gem- 

 mules they are absent; hardly the gemmules have germinated, 

 hbtvever, and the number increases again. The number of the colour- 

 less algae with structure is small and remains rather constant 

 during development, showing a considerable decrease during and 

 after the gemmule stage. The 7iumber of the colourless ones without 

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

 siderably afterivards, also showing a strong decrease (as far as 

 ive may judge) during or after the gemmule stage. 



3. In the course of the developmient of the tissues of colourless 

 Spongillae the number of the green algae remains constantly small, 

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

 however, the gemmules have germinated the number immediately 

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

 very small; as a rule they are even missing. TJie number of the 

 colourless algae with structure is not great and remains rather 

 constant during development, showing a considerable decrease during 

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

 without structure is rather great at the beginning and increases 

 considerably afterwards, also showitig a great decrease during and 

 after the gemmule stage. 



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

 gillae as u'ell 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 immediately after the gemmule-stage the tissue of 

 a Spongilla contains a minimum of green and colourless algae. 



6. In the green sponges the number 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 number of the gree?i algae is 

 always much smaller than that of the colourless ones together. 



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

 numerous than in the colourless sponges. 



