634 THE POPULAR SCIENCE MONTHLY. 



hauled in, turned inside out, and rinsed by immersion and agitation in 

 a bucket of water kept in the bottom of the boat. In this way every- 

 thing entangled in the meshes of the net is transferred to the pail. 

 The net is again put out and the operation repeated. 



Skimming may be performed at any hour of the day ; but in the 

 daytime the forms collected will differ considerably from those capt- 

 ured at night, and, besides, will not be nearly so numerous. The 

 best place for skimming is a spot where two tidal currents meet, form- 

 ing a line of scum upon the surface ; the best time is in the evening, 

 when the surface of the water is calm and smooth. Then the wealth 

 of forms and individuals is almost incredible, and no one who has never 

 seen the operation can have the slightest conception of the results. 

 Each time the net is hauled from the water it shines like molten gold 

 from the phosphorescence of the myriads of animals by which it is cov- 

 ered. On closer examination it is seen that spots of other colors exist 

 among the prevailing yellow light : bright red, blue, bluish-green, 

 emerald-green, and white occur, and after some experience one learns 

 to recognize the presence of a few species by the color of the light. 



Only two or three hauls of the skimming-net are necessary to insure 

 an abundance of material for study, and at no time need the student 

 spend more than half an hour in this work, while frequently ten or 

 fifteen minutes are ample. The laboratory is now sought, and the 

 contents of the bucket in which the net was rinsed are poured into 

 shallow glass dishes placed between the student and a lamp. Then, 

 and not till then, does one begin to realize the enormous amount of 

 life in the sea. In half an hour's skimming not a thousand gallons of 

 water will pass through the net, and yet but a single glance at the 

 dishes convinces one that millions — yes, millions — of individuals have 

 been captured ! The water is roily with minute animals and embryos, 

 whirling, dancing, and jerking about in the strangest manner. 



On different nights the relative proportion of forms will vary. To- 

 night not a single specimen may be taken of a species which last night 

 was very abundant ; but at all times a large proportion of the captures 

 will be found to be copepod crustaceans — small forms not over a quar- 

 ter of an inch in length, which swim about in a jerky manner by 

 means of violent strokes of their long antenna?. To enumerate all the 

 forms which might be taken by skimming would prove a difficult task, 

 but some of the more prominent forms are readily recognized by the 

 peculiarities of their motions. ' The Crustacea move by jerks, the em- 

 bryo worms and mollusks, on the other hand, whirl away in a mazy 

 waltz ; while the jelly-fish swim lazily away by the languid contrac- 

 tions of their umbrellas. 



While a general view of the results of surface-skimming is interest- 

 ing and instructive, our student has other work before him. He is to 

 take one species of embryo and follow it through its transformations - 

 Soon after the dishes are placed before the light, most of the forms will 



