28 SPONGES 3 
of the twig, we can ascertain whether a sponge is growing in any particular di- 
rection or not. 
Of course as the skeleton is formed from the sarcode, or sponge flesh, this 
always grows in advance of the horny fiber. ‘This fleshy matter is rather more 
dense around new fiber, especially about the tips of the growing twigs. When 
division of the twig is about to take place, this thicker sareode becomes more 
bulbose about the extreie tip of the growing twig than at other times, and in 
this bulb the division of the twig occurs. (See Fig. 16, C,a, where there is 
a divided twig, and compare with b, in which division is not taking place. ) 
I may here say, in passing, that the best way to examine the skeleton for + 
new growth is in an alcoholic specimen. ‘The flesh may be easily removed, 
bit by bit, with a needle, taking care not to break the delicate terminal fibers. 
But although it is quite easy to satisfy one’s selfas to the method of growth, it 
is not always easy to find a twig in the act of dividing, I have, however, 
found several, and have a number of times traced a complete series from the 
very earliest division to the point of anastomosis or to arrested growths. 
The growth at the terminal portion of the tube is most rapid, and of course 
upward and slightly outward, but never inward, and branches of the fiber con- 
tinue to grow, sending cut many twigs before any anastomosis takes place. Or 
in other words, that portion of the cylinder which is the most advanced, produc- 
es branching fibers which push upwards without anastomosis ; fibers which send 
out lateral branches are the ones which anastomose. Anastomosis appears ta 
take place by the tip of one growing twig coming in contact with the side of 
of another growing twig. This combination must take place near enough to 
