Dr. G. C. Wallich on the Diatomacea?, 5 



easily explained. Such are the facts, however ; and the means by 

 which these bodies are so widely distributed are inscrutable, un- 

 less it be ultimately determined that they are in great part purely 

 pelagic examples of the orders and genera to which they belong. 

 This appears to be the most consistent view of the matter, seeing 

 that the agency of drift-weed, or any other fortuitous cause, 

 would be quite inadequate to produce so vast a result, even so 

 far as mechanical dispersion is concerned, not to complicate the 

 question with the more important part of the problem, namely, 

 the preservation of the vitality and integrity of the beings under 

 consideration/' 



I can most fully verify Mr. ]\IacdonakFs observations, having 

 detected in the open sea, and widely distant from land or drift- 

 weed, vast assemblages of minute animal and vegetable life, 

 embracing every order to which he makes reference. My own 

 observations, carried on during the voyage from Calcutta in the 

 spring of the same year in which Mr. Macdonald's paper was 

 published, led me to the following conclusions : — 



That an inconceivable multitude of minute animal and 

 vegetable organisms, the remains of which have been detected 

 in deep-sea soundings, are, in their normal living state, 

 strictly free-Hoating forms, inhabiting an extended bathyme- 

 trical range in the waters of the ocean. That the limits and 

 variation of this bathymetrical range are determined by causes 

 having reference partly to the condition of the atmosphere, and 

 partly to the peculiar idiosyncrasy of the organism in c^uestionj 

 the two sets of causes being influenced mutually, one by the 

 other. Tliat these floating pelagic forms constitute the principal 

 source of food for the countless millions of minute animals which 

 inhabit the open sea. And, lastly, that to the combined opera- 

 tion of such animals and those mightier zoophagists to whom 

 the latter atoms afford, in their turn, a prolific prey, the sub- 

 marine deposits of silicious and calcareous remains are, in a chief 

 degree, attributable, the effects of natural death and decay being 

 duly taken into consideration*. 



* The late Professor Bailey of New York states ( Journ. ^Microscop. Soc, 

 vol. iii. p. yO) that Lieut. Berrjnian of tlie United States' Navy found " no 

 trace of hard-shelled animalcules from specimens of water taken either 

 at the surface or at any depths, at situations in close proximity to the places 

 where the soundings were made, in the summer months, when animal life 

 is most abundant ;" and that "the animals ])resent," some of which were, 

 at the time of writing, "alive in bottles, were all of a soft, penetrable nature, 

 leaving on their decay oidy a light floeculent matter, while the I'oraminifera 

 and Diatoms would liave left their hard shells, if they had been jn-esent." 



It is needless to say that these observations are quite inex])licable, unless on 

 the assumption that the means necessary for the capture of all the smaller 

 inicrosco])ic organisms were inadequate. At all events, a diametrically 

 opposite result has been recorded by other observers. 



1* 



