SPONGES 99 
the termination to have the inner membrane naked or not coverd even with a 
single layer of horny matter, then a perfect anastomosis takes place; that is. 
the tip of the anastomosing fiber absorbs that portion of the other’s tubular 
membrane with which it comes in contact; thus the hollow becomes continuous 
from one fiber to another. The growth of the twig coming in contact is at once 
checked and horny matter is deposited over the place of jointure. (See Fig. 14 
where I give three examples of the anastomosis of growing twigs at A, B, and 
C; 0, being the point of jointure, and as will be seen this is not always at the 
same angle, that at B being at right angles, that at C being obliquely down- 
Fic. 17. 
Illustrating the skeleton of Tube Sponge. A, B, arrested twigs with 
secondary growths, C, twig arrested just after dividing. D, arrested twigs from 
external surface. F, G, J, same from surface of central tube. H, and above. 
the same with cuplike depressions. K and §, portion of skeleton enlarged four 
times. M andN, flattened fibers from the filamentous growth. FE, arrested 
twig which came in contact with a hard surface. 
