l6O PAUL S. GALTSOFF. 



mixed suspension. Examining after 24 hours such a clump of 

 Microciona and Cliona one can find that in a common yellow 

 mass of Cliona cells the Microciona had formed globular aggre- 

 gates with marked membranes separating them from cells of the 

 other species. 



The formation of the aggregate in a mixed suspension does not 

 go so completely as in a pure one; the aggregates are smaller and 

 correspondingly more numerous than in the control dish. They 

 are unable to undergo further transformation. 



The coalescence of the dissociated tissue cells of sponges is 

 apparently the same phenomenon as occurs in the extravasated 

 blood cells of Arthropoda (Tait, 1918, Leo Loeb, 1920). In 

 both cases the mechanical or chemical changes in the environ- 

 ment of the cells lead to its amoeboid activity and to formation 

 of aggregates of separated cells. In sponges the archaeocytes 

 i.e., non-specialized elements, form aggregates which are able 

 to regenerate a new organism. In blood cells the process does 

 not go so far; the amcebocytes join in clumps and under favora- 

 ble conditions can form a certain kind of tissue (L. Loeb). There 

 is no indication of chemotropic or cytotropic stimuli in both 

 cases and no such hypothesis is required to explain the results. 



CONCLUSIONS. 



The coalescence of separated sponge cells is the result of two 

 factors: first, amceboid activity of the archaeocytes, second a 

 specific physical property of cell protoplasm which enables the 

 cells to coalesce when they come into contact. 



The coalescence of cells of two different species never occurs 

 apparently because the physical properties of the protoplasm 

 of the various species are different. 



So-called cytotropism or a special kind of chemotropism does 

 not exist in the cases studied. 



REFERENCES. 

 Huxley, Julian S. 



'21 Differences in Viability in Different types of Regenerates from Dissociated 



Sponges, with a Note on the Entry of Somatic Cells by Spermatozoa. 



BIOLOGICAL BULLETIN, Vol. XL., No. 3, p. 127-129. 

 Huxley, Julian S. 



'20 Further Studies on Restitution-bodies and free Tissue-culture in Sycon* 



Quarterly Journal of Microscopical Science, Vol. 65, New Series, p. 



293-322. 



