MICROSCOPE AT THE SEA-SIDF. 69 



CHAPTER V. 



A HALF-HOUB WITH THE MICEOSCOPE 

 AT THE SEA-SIDE. 



ON a visit to the sea-side, the Microscope is an 

 essential instrument to all who would wish to 

 study the wonders of the ocean. It is a curious 

 fact, that the few grains of common salt in the 

 gallon of sea-water seem to determine the exist- 

 ence of thousands of plants and animals. We shall 

 therefore find living in the sea-water, plants and 

 animals belonging to the same families as those 

 in fresh water, but belonging to entirely different 

 species. 



The sea-weeds present strikingly different forms. 

 Although many of them are microsopic, and belong 

 to the families of Diatomacece and Confervacece, all 

 the larger forms present interesting objects for 

 examination in the structure of their fruit-bearing 

 organs. No better subject for the latter purpose 

 can be procured than the common bladder-wrack, 

 which is so abundant on all our shores. If a frond 

 of this fucus is examined, there will be found at 

 certain parts a swollen mass, dotted over with 

 round yellowish bodies. If one of these is taken 

 and carefully pressed between two pieces of glass, 

 it will present the spores surrounded with hairs 

 of the most delicate and various structure. Some of 

 the spores are divided into four parts, and on this 

 account are called tetraspores. These are seen at 

 d, figure 111, plate 4. The bladder-wrack is fre- 

 quently covered with minute parasites ; one of the 

 most common of these is Polysiphonia fastigialcl, 



