attractive work of Dr. Henri Van Heurck on the diatoms of 

 Belgium forms a monograph on tiiis subject, and the Ameri- 

 can student should possess this work or have access to it in 

 his own researches, for the help it affords is very considerable. 

 Assistance will be obtained in the Annual Geological Rei)ort 

 of Indiana, 1882, in the paper and plates contributed by 

 Rev. Geo. L. Curtiss. 



The more inviting field of protozoan investigation is for- 

 tunately occupied by ac exhaustive writer, and the young 

 microscopist will rejoice in his first amazement over these ex- 

 traordinary and prevalent forms, totui'ntothe sumptuous 

 work of Dr. Leidy upon the Fresh Water Rhizopods of 

 America. 



Infusorial life has been treated upon with abundant ela- 

 boration and apparently* delightful literary skill and attract- 

 iveness by W. Saville Kent. These multitudinous objects, 

 whose swarming numbers and eccentri- motions early at- 

 tracted the attention of observers, in old works are describ- 

 ed as animalcula, a name which popularly still clings to 

 them. Antony Van Leeuwenhoek in 1677 published the 

 first account of these interesting forms, whose myriads per- 

 vade the waters about us, and his work was followed by 

 Baker (1742), Muller (1773), and others. Veritable progress 

 in the understanding of the real position of mfuf<oria proper 

 and in the separation of ihe heterogeneous group of objects 

 included under the name of animalcula was made by Ehren- 

 berg, Dujardin(1811), Von Siebold (1845), Stein (1854), Cla- 

 parede au^iLachmanu (1858), Max Schultze (1860), Pritchard, 

 and among modern auihors by Haeckel, Englemann, and 

 Butschli (Nature, vol. xxvii. p. 601). 



The work of Mr. Kent is comprehensive to the last de- 

 gree, and though his views as to the generation of infusoria 

 and their affinUies have encountered adverse criticism, his 

 lists and descriptions of species and.his figures are simply un- 

 excelled and invaluable. 



The bibliography of rotifers is quite large, and is not con- 

 fined to any special work ; Carpenter, Gosse, Ehrenberg, 

 Dujardin, Pritchard, etc., having contributed to this section 

 of microscopic study. 



For the Crustacea the student will find less convenient and 

 complete works at his command. Two notable contribu- 

 tions, monographic in character, to this subject, have been 

 published by Prof. A. S. Packard and C. L. Herrick. Prof. 

 Packard's work is contained in the Annual Report of Hay- 

 den's Survey of the Territories, for 1878, part i. and treats 

 of the subdivision of phyllopods whose forms prevail in the 

 AVest and are sparingly represented in our Eastern regions. 

 Mr. Herrick's work represents the results of careful research 



* The wrilers do not possess a^ yei a copy of tbis expensive work, 

 thouj^h ihey will soon doubtless liave access to it. 



