CALCAEEOUS SPONGE. 23 



The specimens which are to be presented in alcohol 

 should be placed in seventy-five per cent alcohol as soon 

 as possible, and left for about twenty-four hours. They 

 should then be transfeired to eighty or eighty-five per cent 

 alcohol, and left in that for about twenty-four hours, and 

 they may then be preserved, until they are wanted, in 

 ninety or ninety-five per cent alcohol. 



The other specimens should be placed in a shallow pan 

 or dish filled with a saturated solution of picric acid, and 

 left for about ten hours. They should be transferred to 

 seventy-five per cent alcohol, in which they should be left 

 for about twenty-four hours, when they may be put into 

 strong alcohol ninety or ninety-five per cent. In about 

 twenty-four hours this alcohol should be poured off and 

 renewed ; and at the end of another day, if the alcohol has 

 turned yellow, it should be again renewed; and so on, 

 until the alcohol remains colorless. Examine one of the 

 alcoholic specimens in a watch-crystal full of alcohol with 

 a hand-lens, or with a very low power of the microscope, 

 — ten or twenty diameters, and notice : — 



I. The External Form. 



a. The brown, cylindrical or vase-shaped body. 

 h. The opening, or oseulum, at its distal or free end. 

 c. Smaller sponges, which have been formed by bud- 

 ding around the proximal end or base of the larger one. 



II. Split the specimen with a razor or sharp scalpel 

 through the long axis of the body, thus laying open the 

 central cavity or cloaca. Examine the cut surface with a 

 very low magnifying power or with a hand-lens, and 

 notice : — 



a. The body cavity, or cloaca (Fig. 13, g), a large 

 cylindrical cavity, which occupies the long axis of the 

 sponge. 



