DEVELOPMENT OF SPONGES FROM DISSOCIATED TISSUE CELLS. 25 



A large branched Microciona was selected. It was divided into a few parts. One 

 of these was chopped up and strained. The extruded tissue was sown on slides. The 

 preparations developed quickly and were put in live box July 3. On July 4 canals had 

 developed in them. 



Two days later the other pieces of the Microciona were chopped and strained and 

 the tissue sown on slides. The tissue quickly collected in shape of rounded and irregular 

 masses. These do not combine with one another to any extent and do not flatten out. 

 The tissue remains in this condition for a couple of days in the laboratory. Some of 

 the preparations were then hung in the live box. Much of the tissue died, but a con- 

 siderable number of the masses flattened and metamorphosed. Other preparations 

 were kept in laboratory dishes for a few days longer. They underwent no visible change- 



ADDENDUM. 



April 17, igii. 



I am fortunately able to take note of the progress that has been made in this field 

 of inquiry while the foregoing paper was in progress of publication. 



Miiller, working on the SpongilUdae," confirms my account of the behavior of dis- 

 sociated cells in sponges. The phenomena are essentially the same in these sponges 

 as in the marine forms I have studied, and Miiller has been able to rear perfectly formed 

 Spongillas in this way. He has kept some of his Spongillas alive in confinement as 

 long as seven weeks. It is to be hoped that he will find the time to carry on a 

 detailed histological study of the cellular changes involved in this method of regenera- 

 tion, a side of the subject on which my own observations are very fragmentary. 



Miiller has also been able, again working on the Spongillidae,'' to confirm the essen- 

 tial points in my investigation (intimately linked with the present and leading up to it) 

 on the formation of masses of regenerative tissue in sponges that are kept in confine- 

 ment." Miiller finds as I did that in sponges kept for a considerable time in confinement 

 a slow process of regressive differentiation takes place, resulting finally in the production 

 of masses of a simplified or "embryonic" tissue. Such regressive differentiation would 

 fall under the currently employed rubrics "involution" (Barfurth) and "reduction" 

 (Driesch and Eugen Schultz). 



The early steps in the process (contraction of body, gradual suppression of canals, 

 dissolution of flagellated chambers into their constituent cells which become despecial- 

 ized, division of the body in this simphfied state) all seem to be identical in the Spongil- 

 lidae and in Stylotdla, the marine form which I especially studied. The differences 

 concern the later stages and consist (i) in the absence of any extensive death of the 

 sponge body in the Spongillidae and (2) in certain interesting histological features of 



a Miiller. Karl: Versuche tiber die Regenerationsfahigkeit der SusswasscRchwamme. Zoologischer Ajizeiger, bd. xxxvn, 



nr. 3-4. 191 1. 



i> Miiller. Karl; Beobachtungen iiber Reduktionsvorgange bei SpongiUiden, nebst Bemerkungen zu deren ausseren Mor- 

 phologie und Biologic. Zoologischer Anzei^ier. bd. xxxvn. nr. 5. 1911- 



c Wilson, H. v.: A new method by which sponges may be attifidally reared. Science, n. s., vol. xxv. June 7. 1907. 



