RESTITUTION-BODIES AND FREE TISSUE-CULTURE IN SYCON 295 
tion, and the organisms and thew parts appear to be more 
delicate. 
The method originally adopted was that discovered by 
H. V. Wilson—the squeezing of the chopped-up sponge through 
fine-meshed silk bolting-cloth. 
In order to procure * pure cultures ’ of collar-cells, the sponge 
or a transverse segment of it is held with one needle and briskly 
teased with another. By this means large sheets of collar- 
cells are obtained. If the pieces are shaken together in a solid 
watch-glass, they will cohere and larger masses result. 
A method which will give an excess of collar-cells but not 
an almost pure culture is simply to perform the teasing process 
as above, and then remove the portions of original sponge. 
The collar-cells, being more easily detached than the others, 
will form the bulk of the tissue present. 
Kinally, simple squeezing of the whole sponge with the 
fingers into water will give a thick suspension of single cells 
and very small cell-aggregates, which is very similar to the 
culture produced by squeezing through gauze. By different 
dilutions of this suspension, different results can be achieved. 
These methods will be called squeezing through gauze, 
choanocyte isolation, teasing, and squeezing without gauze 
respectively. 
The experiments at Wood’s Hole were done in late July 
und August ; those at Plymouth in July and early August. 
3. SUBDIVISION OF RusTITUTION-BODIES. 
(Work done at Plymouth.) 
A teased culture was made on August 3, 1920. Many of 
the restitution masses were of rather large size. They began 
to blow out in normal fashion, and after six days a number of 
very fine choanocyte blow-outs were present. On the seventh 
day they were even better. On the eighth day a certain 
quantity of bodies consisting of a number of small spherules, 
rather closely packed together, were observed in the dish 
(fig. 1). They were attached to the glass, and some force was 
