350 BULLETIN OF THE BUREAU OP FISHERIES. 



Woods Hole, of which the four most common species were Licmophora tincta, Diatoma 

 hyalinum, Rhabdonema arcuatum, and Tabellaria unipunctata, named in the order of their 

 relative abundance. 



I have seen the fry almost buried out of sight by diatoms in neglected jars at Woods 

 Hole, especially by Tabellaria, which at times was very abundant and destructive. 



Other organisms found by Gorham to infest the young lobsters at Woods Hole were 

 a filamentous green alga and a stalked protozoan, Ephelota coronata, which was more 

 abundant in the waters of Wickford, R. I. 



Caimibalism may be reduced by supplying the yoimg with proper food, by agitating 

 the water and thereby keeping both the young and their food suspended, and by avoiding 

 overcrowding. The growth of diatoms can be checked or prevented, according to 

 Gorham, by filtering the water; by selecting a suitable station for the rearing apparatus 

 where diatoms do not abound, and where the temperature is high or most favorable for 

 hastening growth and molting, by which the little animal escapes for the time being at 

 least from all its troublesome messmates; by frequent cleaning, coating, or renewal of the 

 rearing bags ; and by reducing the light and thus hampering the diatoms by cutting down 

 their food supply. (Compare, p. 281.) 



THE SIGNinCANT FACTS OF LARVAL AND LATER DEVELOPMENT. 



Some of the most important facts concerning the larval life of the lobster may now 

 be summarized: 



(i) The young are hatched in great numbers, 5,000 to 100,000 eggs or young being 

 produced at one time by a single animal according to its size, the number increasing 

 rapidly in proportion to the cube of the body length or to the total volume of the body. 

 This leads us to expect great destruction of the yoimg in nature, an expectation which is 

 unfortunately realized. It is a vulgar error to assume that the abundance of this ani- 

 mal or of any other species is proportional to the number of young bom, since it neglects 

 the equally important question of the destruction of the young or their rate of survival. 

 The rapid rise in production beyond the lo-inch size proves that the older the animal the 

 more valuable it becomes for reproductive purposes, barring the question of sexual 

 decline, which is of little importance in an animal so seldom permitted to grow old. 



(2) The larvae are hatched at the bottom of the ocean in relatively shallow water at 

 night or in early morning. A molt occurs at the time of hatching; parental instinct 

 ceases; the larvae are soon dispersed, and leaving the bottom lead a free-swimming, 

 pelagic existence for a period of from 3 to 6 weeks (see p. 348), according to circumstances. 

 Summer eggs on the coast of Massachusetts are hatched from May 15 to July 15, the 

 majority being extruded in June. 



(3) The movements of the larvae in a natural state are not fully understood. Under 

 certain conditions they rise toward the stronger light at the surface; under other condi- 

 tions they retreat from the light, sinking to greater depths. They have been taken near 

 the surface in the townet in both strong sunlight and at night, both with and without 

 the aid of artificial light. At the present time they are seldom found at the surface under 



