1893.J NEW-YORK MICROSCOPICAL SOCIETY, 113 



the Diatomaceae float on the surface of the seas as a dense 

 foamy sheet and are the sole food of some kinds of fish. The 

 Abbe Castracane, already referred to, has written a special paper 

 on the presence of the Diatomaceae as the sole and exclusive 

 food of Echinus and Echinodermata and Holothurite, dredged 

 by the Challenger from depths of 2,000 and 5>740 metres. His 

 abject was to prove, contrary to common belief at that period, 

 that plant life vegetated at a depth where the rays of the sun 

 never penetrated. The fact of his finding rich masses of Synedra 

 thallassiotrix Cleve. and Coscinodiscus in the Holothuriae and 

 Echini taken from these depths confirmed his belief. As the 

 Abbe was a firm believer in the plant nature of the Diatomaceae, 

 he could not well do otherwise than regard this kind of food as 

 plant life. He proved that the diatoms passed their life cycle at 

 the bottom of the ocean, at 5.740 metres, on the feeding ground 

 of the Echini and Holothuriae, as the endochrome had not been 

 removed by the digestive juices of the Echini or Holothurise 

 after their removal by the dredge from their habitat at the bot- 

 tom of the ocean, thus drawing another illustration of the use of 

 the Diatomaceae as a food supply. 



I would note that at least four of the slides prepared from 

 Mobile Bay brackish-water material, and sent herewith, show a 

 number of rhizopods, Euglypha alveolata, within whose transpa- 

 rent and glass-like shells may be seen several varieties of very 

 minute diatoms — viz., Cocconeis pediculus and Naviailce. Also in 

 a more pronounced manner, in the beautiful plates of Leidy's 

 *' Rhizopods of North America," various amoebae are depicted at 

 the moment of enveloping within their fluent protoplasmic layers 

 large Pinnularice and other diatoms. And I have put upon rec- 

 ord with this Society a selected slide of Difflugia pyriformis and 

 other species, in which minute diatoms are seen to form a part of 

 the solid shell covering the soft pseudopodial parts of the animal 

 protoplasm when in its living state. 



In the slides referred to above a pair of shells of Euglypha 

 alveolata are mounted, showing the mouths of the shells in contact, 

 or in the position usually regarded as that of conjugation. In 

 the same slides will be noted an extraneous class of minute ani- 

 mals found in Mobile Bay — viz., minute shrimp, whose chitinous 



