154 PAUL S. GALTSOFF. 



The writer desires to express his gratitude to Dr. F. R. Lillie, 

 Director of the Marine Biological Laboratory at Woods Hole, 

 for accomodations there and to Dr. T. H. Morgan, of the Depart- 

 ment of Zoology, Columbia University, for the courtesy of ex- 

 tending to him laboratory privileges. 



SPECIES USED FOR EXPERIMENTS. 



The coalescence of cells after their dissociation has been ob- 

 served in many species of sponges. It is probable that all sponges 

 possess this ability, but the formation of dense conglomerates 

 and the power to regenerate a new organism occur only in a few 

 forms. The species tested by the writer are as follows: Black 

 Sea sponges Ilalichondria grossa Schm., Petrosia clavata B. 

 Cor., Reniera densa Bowerb., Reniera informis Schw., Esperella 

 lorenzii Sch., Kowalevskiella gracilis Swarc., Spongelia sp., Sycon 

 sp.; Woods Hole sponges Microciona prolifera Verr., Cliona 

 celata Gr., and Grantia sp. 



Upon dissociation the cells of these species are able to coalesce 

 and to form aggregates, but the grade of the formation varies. 

 The best forms are Reniera informis, Reniera densa, Petrosia 

 coriacea, and Microciona prolifera. The formation of aggregates 

 in these species requires less time, the aggregates are more strong- 

 ly attached to the substratum and they quickly transform them- 

 selves into new sponges. 



Unfortunately many of the microphotographs, drawings, and 

 other data collected by the writer at Sebastopol were lost owing 

 to unavoidable circumstances and therefore the present work 

 deals chiefly with the experiments made on Microciona prolifera 

 at Woods Hole. 



AMCEBOID MOVEMENT OF DISSOCIATED CELLS. 



The suspension of dissociated Microciona cells, obtained by 

 squeezing the sponge through bolting silk No. 20, consists of 

 three classes of cells, each of which can be easily recognized. 

 The most abundant. are the archaeocytes, nonspecialized, reddish 

 cells about 8 microns in diameter and loaded with granules. Two 

 kinds of these cells can be discriminated : the endoplasm of the 

 first contains red pigment granules, to which the red color of the 

 sponge is mainly due; the second contains in addition to a less 



