116 EXPERIMENTAL LESSONS. 



Tail, a little less deeply forked. Flight, graceful. Beneath, white. 

 Size, medium. Bahama Swallow. 



Tail, moderately forked. Flight, heavy. Beneath, dark colored. Size, 

 large. Purple Martin. 



Tail, quite slightly forked. Flight, rather easy. White beneath. Size, 

 medium. White-bellied Swallow. 



Tail, very slightly forked. Flight, quite light and easy. Beneath, white, 

 with dark band across breast. Size, small. Bank Swallow, 



Tail, very slightly forked. Flight, rather heavy and slow. Beneath, 

 white, with throat and neck brown. Size, rather small. Rough-winged 

 Savallow. 



Tail, square, not forked. Flight, heavy and slow. Beneath, reddish, 

 with dark spot on throat. Rump, chestnut. Size, medium. Eave Swallow. 



EXPERIMENTAL LESSONS. 



LESSON ON SPONGES IN A NINTH GRADE, WILLIAMS SCHOOL, 



AUBURNDALE, MASS. 



BY 



John O. Godfrey. 



Sponges, by Anna Lowe. 



The fibers in the sponge are woven closely together. They all grow into 

 one another, and are one continuous line all the way through the sponge. 

 The fibers are hollow in the interior, and if we were small enough to get 

 inside of these fibers we could travel all through the sponge. 



The flesh of a sponge grows first so that it can produce the fibers and 

 every thing that is necessary for the sponge is produced by this flesh. The 

 fibers are composed of horn, and sponge flesh is constantly adding horny mat- 

 ter to these fibers, so that old sponges become thicker than younger ones, 

 and they cannot be as tightly squeezed as the old ones. When the lining 

 membranes of the fibers come together, they run into each other. Salt water 

 sponges put into fresh water will be killed. 



Some people say that sponges are planted. When this is done, the 

 sponge grows from the side which is not cut. When long sponges are grow- 

 ing, they are apt to be broken off, so then they will not grow upward any 

 more, but will grow from the sides. 



