Dr. G. C. Wallich on Desmidiacea from Lower Bengal. 185 



outburst of fresh life to which microscopic forms are subject 

 ill such a chmate, by any comparison with what is observable 

 elsewhere. Immediately prior to the setting in of the annual 

 rains, the swamps, pools, water-courses, and even the majestic 

 rivers, are well nigh dried up. The surface of the soil is parched 

 into a layer of impalpable dust, and the remnants of all the 

 minute tribes of plants are carried to and fro, by the slightest 

 winds, amongst the dusty particles to which they themselves 

 largely contribute. At this period the sporangial state is as- 

 sumed both by the Desmidiacese and Diatomacese, and it may 

 be regarded, therefore, as a species of hybernation, during which 

 vitality is maintained under the minimum of the conditions 

 essential to its continuance, and without the interposition of 

 which phase these organisms would become extinct. For up- 

 Avards of two months the rains continue to fall incessantly. 

 The whole country is Hooded, and the rivers expand to the pro- 

 portions of inland seas. It is useless, as yet, to search for the 

 Desmidiacere. No sooner, however, have the rains and inunda- 

 tions subsided, than the mud-laden pools clear down, the magic 

 influences of light and heat are permitted to operate, and, in an 

 incredibly brief period, the surface, the bottom, and the body of 

 the waters absolutely teem with the crowded masses of animal 

 and vegetable life. 



In endeavouring to classify the various forms, 1 have very 

 reluctantly been compelled, in several instances, to modify the 

 arrangement laid down in ]\Ir. Ralf s admirable Monograph of 

 the Desmidiaceaj. I would mention, however, that there are 

 two or three characters adopted by that author which, as far as 

 my observation of the Bengal forms is concerned, are of too vari- 

 able a nature to be admissible for purposes of diagnosis. Thus, 

 according to the varying periods of growth of the organism, 

 the endochrome may be equably disposed in minute granules 

 throughout the protoplasmic cell-contents, it may be aggre- 

 gated into definitely or indefinitely shaped masses, or it may pre- 

 sent itself in the form of radiating bands, generally answering 

 in number to the number of lobes or angles of the given species, 

 and offering cleft or entire extremities according as the granules 

 have remained dispersed or have coalesced under the molecular 

 law to which they are subject. In some genera the disjjosition 

 of the endochrome must, no doubt, be regarded as highly cha- 

 racteristic, — as, for instance, in Docidium, Penium, TetmemoruSf 

 and Closterium. But even in different individuals of each of 

 these genera, and in the same individual under different condi- 

 tions, it will be found to vary greatly ; and for this reason I 

 have deemed it advisable, as a general rule, to confine my illus- 



Ann.t^ Mag. N, Hist. Ser. 3. Fb/.v. 13 



