138 



THE AMERICAN MONTHLY 



[Jiiiy, 



but if our correspondent desires informa- 

 tion about any particular one we will en- 

 deavor to indicate the proper course. — 

 Ed.] 



MICROSCOPICAL SOCIETIES 



At a meeting of the Microscopical Sec- 

 tion of the Academy of Natural 

 Sciences, of Philadelphia, held May ist, 

 Mr. Edward Potts spoke on the fresh- 

 water sponges and their classification. 



By the use of a number of excellent in- 

 struments kindly provided by the mem- 

 bers of the Section, Mr. Potts was enabled 

 to exhibit a collection of fresh-water 

 sponges, unique in the possession of 

 many new species never before exhibited. 

 Cabinet specimens in boxes, and others 

 prepared for microscopic examination 

 were shown, covering all the recognized 

 genera of this group of organisms, and 

 probably a majority of all species yet 

 described. 



Mr. Potts began his remarks by saying, 

 that the classification of sponges had been 

 very imperfect in most respects, excepting 

 the lime sponges, which are marine, al- 

 though it is not at all improbable that fresh- 

 water lime sponges will yet be discovered. 

 The fresh-water sponges so far as known 

 at present, are silicious. They merge into 

 the keratose or fibrous variety. The 

 spicules are held together by sarcode. 

 The essential difference between fresh- 

 water and marine sponges is that the 

 latter are reproduced by eggs, but eggs of 

 the former, have not been found. The 

 reproduction is by statospheres or seed 

 bodies — formed at different times, some- 

 times early, sometimes late. Many of 

 the Spongilla are branched, others are 

 simply a film upon stones, etc. 



Until very recently, the fresh-water 

 sponges have been grouped under the 

 single genus Spongilla. In the spring of 

 the year 1881, however, Mr. Carter re- 

 vised their classification, and arranged 

 them under five generic heads, three of 

 which are found to have numerous re- 

 presentations in this country; and two 

 others apparently peculiar to North 

 America have been added. 



This classification is based upon the 

 characteristics of what may be called the 

 third class of spicules, or those pertaining 

 to the statospheres or winter eggs of the 

 sponges. The genera may named and 

 briefly described as follows : — 



I. Spongilla. — Spicules of the stato- 



s])here acerate (needle shaped), straight or 

 curved, smooth or spined, lying upon the 

 chitinous coat. ' 



2. Meyenia. — Sjiicules birotulate, that 

 is, consisting of two wheels or disks, con- 

 nected at their centres by a short shaft. 



J. Heieromeyenia. — Spicules in two 

 series, one of which resembles that of the 

 last genus ; the other is composed of 

 interspersed spicules fewer in number and 

 about twice the length of the former ; 

 generally terminated by strong, recurved 

 hooks. 



4. Tubella. — Spicules inequibirotulate, 

 the outer rotule, or disk, having been re- 

 duced to a fraction of the diameter of the 

 other. 



J. Parmula. — In this the outer disk 

 has become entirely eliminated, leaving 

 the spicules to appear as a series of cones 

 terminated by sharp points. 



6' Carterella. — The form of the spicules 

 in this would place the species amongst 

 the meyenia, but there is superadded a 

 feature not yet observed in connection 

 with any sponge of the old world, which 

 demands for it a distinct generic posi- 

 tion. This is the possession of a number 

 of cirrous appendages resembling long, 

 curling or twisted tendrils, which are ex- 

 tensions of the chitinous coat of the 

 statospheres, mostly from the neighbor- 

 hood of the foraminal aperture. 



The remaining genus can hardly be 

 said to be well defined, as no statospheres, 

 have yet been discovered. 



Mr. J. O. Schimmel then exhibited a 

 slide containing the flower of Crysosple- 

 nium Americana. 



This delicate flower which is apparently 

 devoid of beauty, when v iewed by 

 the microscope, presents one of the most 

 interesting and beautiful objects that can 

 be shown. 



Mr. Jacob Binder, exhibited four speci- 

 mens of the legs of beetles belonging to 

 two genera of the Coleoptera, Dytiscus 

 marginalis, and Arcelius mediatis from 

 the Hammondton ponds of New Jersey, 

 and Arcelius fraternus, a European 

 species. 



These objects were intended to show the 

 formation of the sucking-cups, found up- 

 on the forelegs of the different varieties. 

 They are only upon the forelegs, except 

 in the case of the Dytiscus marginalis,. 

 where they are also found upon the mid- 

 dle legs in a less developed condition. 

 These suckers are sufficiently destinctive 

 in their character to assist the ento- 

 mologist in their classification. 



