62 VIEWS OF THE MICROSCOPIC WORLD. 



tected in the mud of Boston harbor, and in the marine marshes at New Haven in 

 Connecticut ; and numerous elegant infusorial structures and many-chambered 

 shells, have been found at Amboy in New Jersey, in the mud adhering to oys- 

 ters as they were taken from their beds. 



In view of facts like these, it has been asserted by naturalists, that the de- 

 posits in harbors, and the accumulation and amazing fertility of the mud of the 

 Nile, and probably of other turbid rivers, are to be attributed in a great measure 

 to the agency of invisible animal life, whose countless generations succeed each 

 with astonishing rapidity, leaving the curious structures in which they resided as 

 the durable records of their existence. 



These gradual accretions have been accumulating for centuries, and are at this 

 moment still in progress. The sea now swarms with races of minute animals, 

 whose fossil types are continually discovered in beds and strata of unknown an- 

 tiquity. In salt water, taken from Cuxhaven and various other places, no less 

 than twenty genera and forty living species have been discovered by Ehrenberg, 

 which he regards as identical with those occurring in the chalk formations. And 

 out of twenty-eight species of fossil Infusoria belonging to the Bacillaria or stick- 

 animalcules, he has detected fourteen fresh water and five marine species, now 

 living ; the remaining nine are either unknown or extinct forms. 



The Infusoria that crowd the seas are devoured in multitudes by the common 

 scallop and other molluscous animals ; for when their stomachs are examined 

 they are found to contain thousands of microscopic flinty shells, which, from 

 their nature, were incapable of being digested. When a few atoms of the food 

 which a scallop has taken into its stomach is viewed by the microscope, it is 

 found teeming with a rich collection of Infusorial shells, closely resembling 

 the beautiful structures that constitute the Richmond deposit, not only in form 

 but in arrangement so striking is this resemblance, that it is said to be 

 extremely difficult to distinguish between the recent and ancient remains ; and 

 that even an experienced observer would be liable to confound them, unless the 

 glass slides, upon which they were mounted, were labeled. 



The guano imported from the isle of Ichaboe has been found to contain the 

 beautiful shell of the Coscinodiscus, and other Infusorial structures of great 

 elegance and richness ; and, as we gaze upon these minute cases, we cannot fail 

 of being struck with the fact of the great resistance to decomposition which 

 they possess. In this instance they must have gone through the process of di- 

 gestion twice, and been subjected to the action of the elements for centuries. 

 Guano, as is well known, is found within certain latitudes on uninhabited islands, 

 which have been, for ages, the abode of innumerable multitudes of marine-birds. 

 It consists of their excrements, which have been accumulating for century after 

 century, until they form layers of great thickness ; many beds having been dis- 

 covered in the islands of the Pacific, off the Peruvian coast, having a depth of 

 thirty-five or forty feet. The Infusorial shells, detected in the guano, are the 

 remains of animalcules devoured by fish, which, afterwards, became the prey of 

 voracious sea-birds. Thus the shell passed through the stomach twice, and then 



