FISH ANIMALCULES. 9 



guishable from the darkness of nonentity. The Monads are, for 

 the most part, of a round or oval form, and in all the larger kinds 

 a distinct tail-like appendage is discernible, which was supposed 

 to be at once an organ of motion and a means of obtaining food. 

 One tribe, however, which was included in the genus Euglena, 

 bear a close resemblance to fishes in shape, and being provided 

 with a large red eye-spot, they pass very well for " Fish Ani- 

 malcules." It frequently happens that these tiny representatives 

 of the finny tribes are congregated in such vast profusion as to 

 impart to the water in which they occur a very perceptible tinge 

 of colour ; and Ehrenberg fancifully suggests that it was probably 

 by the agency of one of them, which from its colour has earned 

 the name of Euglena sanguined, that the miracle recorded in 

 Exodus, of turning the waters of the Nile into blood, was effected. 

 The commonest of these Fish Animalcules in our own ponds and 

 ditches is E, viridis, which, with its grass-green body and its 

 carmine eye-spot, is a pretty object in the microscope, and one 

 that may be observed with great interest, even tliough we may 

 no longer believe with Ehrenberg that its " eye " is a real visual' 

 organ, or that the clear spaces within its body constitute a lond 

 fide digestive apparatus. 



In the heat of summer, the surface of stagnant pools often 

 becomes covered with a thin film of scum, which looks to the 

 naked eye like a coating of fine dust, but which, on being care- 

 ful ly removed and examined by the aid of a powerful microscope, 

 is seen to consist in great part of various minute organisms, 

 which, when disturbed, move briskly about in the water. A 

 large proportion ef the number are Fish Animalcules of the kind 

 just alluded to ; but, in addition to these, there are others of a 

 larger size, closely allied to the Monads, but presenting some 

 most extraordinary complications of structure. They are in fact 

 compound structures, consisting of Monads grouped together in 

 clusters, and imbedded in the interior of variously shaped gela- 

 tinous masses, which swim about by the united action of their 

 tail-like appendages. One of the most curious of these is the 

 Oonium pectorale, commonly called the High Priest's Breast- 

 plate, which consists of a combination of sixteen monadiform. 

 bodies, disposed regularly in a four-cornered tablet, like the 

 jewels in the breastplate of the Jewish high priest. Another, 

 and still more beautiful variety, is the Pandorina morum, in 



