168 
Journal of the Mitchell Society 
[ December 
paper 5 has emphasized the importance of these unspecialized 
cells in the process of growth and regeneration. His con- 
clusions which refer directly to fresh water sponges, are that 
in a growing sponge, in a sponge regenerating new organs 
after its winter period of simplification, and in the regenera- 
tion of a sponge from a cutting, the amoebocytes are the all- 
powerful elements in that they give rise to all the new tissues 
formed. He further alludes to the fact that such reproduc- 
tive bodies as the gemmules of fresh water sponges and the 
buds of Tethya (according to Maas) are only groups of amoe- 
bocytes; further that the gemmules of Tedania and Esperella 
described by Wilson as developing into ciliated larvae, and the 
similar bodies found by Ijima in hexactinellids, are such 
groups. I may add that the presence of such groups of 
unspecialized cells in the hexactinellids has recently been con- 
firmed by the master in sponge-morpholagy, F. E. Schulze, 
who recogn/zes the probability of their reproductive nature 
and gives them a new name, that of sorites . 6 It is clear then 
that in many sponges reproductive bodies are formed by the 
association of unspecialized amoeboid cells. But there is 
nothing in this fact which precludes the possibility that the 
groups of amoebocytes are in part recruited from transformed 
collar cells and other tissue cells, such as pinacocytes (flat 
cells of canal walls), that have undergone regressive differen- 
tiation into an unspecialized amoeboid condition. 
Cells analogous to the amoebocytes of sponges are found 
elsewhere in the metazoa, e. g., in the ascidians . 7 It would 
be interesting to know what capacity, if any, for develop- 
ment they have, when freed from the parent (bud) and col- 
lected together in sea-water. 
5 Spongilliden-studien V. Zur Biologie von Ephydatia fluviatilis und die 
Bedeutung der Amcebocyten fur die Spongilliden. Archiv fur Naturge- 
schichte, 73 Jahrg., iBd., 2 Heft, 1907. 
6 Wissensch. Ergebn. d. Deutsch. Tiefsee-Exp. 1898-99. Hexactinellida, 
pp. 213-15. Jena, 1904. 
7 Comp. Hjort’s and Lefevre’s papers on budding in ascidians. 
