268 THE MICROSCOPE. 



minute and curious animals, and sometimes Diatomacece, may be col- 

 lected in a similar way. 



Having thus surveyed the rocks, sands, and weeds of the shore 

 above low-water mark, if we launch upon the deep itself a similar 

 abundance of minute and interesting forms is still presented to us. A 

 small muslin bag, the mouth of which is kept open by a wire ring 

 about four inches in diameter, towed slowly behind a boat, on a calm 

 and bright day, in any sheltered bay or inlet, will be found to have 

 gathered multitudes of creatures of the most beautiful forms, and 

 occasionally of the most brilliant colours, creatures whose crystalline 

 substance affords to our wondering gaze a ready insight into many 

 things connected with the structure of the lower animals, which will in 

 vain be sought elsewhere. In this way are collected the numerous 

 species of minute Naked-eye Medusae. 



Nothing can be conceived more elegant and graceful than the 

 motions of these minute crystalline bodies in a glass of water. On 

 almost every part of the coast, besides the beautiful Tunis neglecta and 

 the allied Beroes, the towing- net will gather innumerable specimens of 

 a creature resembling a slender spicula of glass, about an inch in 

 length, but which is so slender and transparent as to be almost invi- 

 sible except in a particular direction of the light : this is the Sagitta 

 bipunctata; and its simple structure affords an excellent subject for 

 microscopic research. When fishing for objects of this kind, it is best 

 to have in the boat a large white basin half filled with sea water ; and 

 into this the towing-net is to be inverted and gently shaken every now 

 and then. In this way the delicate creatures it contains will come out 

 of it without injury ; and though themselves perhaps at first wholly 

 invisible, their shadows will be seen with great distinctness at the 

 bottom of the basin ; and thus many forms which might otherwise 

 escape observation be rendered evident. 



The microscopic wonders of the sea, however, are still far from 

 being exhausted ; it presents as many, if not more, curiosities at the 

 bottom, where its depths are never opened to view, than at the surface. 

 The best and most convenient mode of obtaining these, is by the use 

 of an instrument, with which all perhaps are acquainted in one shape 

 or another, we mean the dredge. 



The essential qualities of a microscopist's dredge are, a small and 

 convenient size, with sufficient weight to ensure its sinking to and 

 keeping at, the bottom, even when at a considerable depth and drawn 

 with some velocity through the water. The dredge we should recom- 

 mend is made of cast iron, which reduces the cost considerably ; and it 



