168 PROCEEDINGS OF THE ACADEMY OF [1887. 



no account left to lie long in the water after being gathered. Pre- 

 serve from dust in covered boxes. 



For the determination of species, a few general directions may 

 suffice, and even these will be soon modified to suit the tastes or 

 the ingenuity of the worker. It is assumed that the investigator 

 has already noted the general appearance of the sponge in hand; 

 its color, size, compactness ; whether simply encrusting, or cushion 

 like ; sending out finger-like processes etc. These indications may 

 help an experienced collector to a guess ; but there are very few 

 species that even such a one could name, with any confidence, be- 

 fore he had made and examined microscopic preparations of the 

 same. 



A stand, supporting a dozen or more test tubes, say three fourths 

 of an inch in diameter by an inch and a quarter in de2:)th ; a drop- 

 ping bottle containing nitric acid, and the usual materials and 

 apparatus for mounting in balsam, are all the appliances needed. 

 As the processes to be described are certain to disturb the normal 

 relations of the several classes of spicules to each other, it is well 

 before the dried specimen has been much handled, to separate some 

 clean portions of the outer or dermal film, lay them upon a slide 

 and mount in balsam without further preparation. An examination 

 of this may determine the presence and decide the character of the 

 dermal spicules, if there are any pertaining to the species in hand. 

 This precaution is necessary in view of the displacement of parts 

 just mentioned, and also on account of the indiscriminating habit 

 of the sponge-currents during life, which almost necessarily charge 

 the tissues with various foreign particles, including vagrant spicules 

 of its own and neighboring species. In practice, the rightful presence 

 of dermal spicules in any species is often so doubtful, that it can 

 only be settled by an examination of young sponges, grown under 

 observation, from isolated statoblasts, whose identity has been satis- 

 factorily determined. 



Next, separate from the sponge some minute fragments, contain- 

 ing skeleton spicules, the dermal and interstitial tissues and a dozen 

 or more gemmules. Place several of the last named with a few ad- 

 herent skeleton spicules upon the centre of a fresh slide, bring to 

 the boiling point in one of the test tubes, five or six drops of nitric 

 acid and by the aid of a dropping tube apply a single drop of the 

 hot acid to the gemmules upon the slide. While the acid is par- 

 tially destroying their cellular or granular crust, pour the remaining 



