REPORT OF COMMISSIONERS OF INLAND FISHERIES. 125 



Parasitic growth. — The dangers from diatomaceous, fungous, and 

 similar parasitic growths are especially serious when the time between 

 molts, due to cold water or poor food, is relatively long. For this 

 reason the temperature is a factor to be considered, when possible, 

 in locating a hatchery. At our station the duration of the whole 

 larval period is from nine to (rarely) twenty-one days, most of the 

 larvae hatching in about twelve to fourteen days. We have found 

 that shading the cars, as Professor Gorham recommended, seems to 

 prevent to a marked degree the growth of diatoms, and also that in 

 the wooden cars recently adopted the annoyance from this source is 

 very slight when the cars are shaded. The insides of all of the boxes 

 were painted, four of them white and the rest green. We could not 

 see that either color had an advantage, judging from the output of 

 fry. Whether the comparative immunity from diatoms of fry in 

 boxes as compared with those in canvas bags was due to the painted 

 surfaces of the wooden sides or to some other factor it is difficult to 

 say. Animal growths, barnacles, molgulas, oysters, mussels, etc., 

 were abundant even on the painted surfaces, and were scraped off 

 each time the cars were raised. Canvas screens on frames (Fig. 7) 

 set up like the sides of a roof so as to afford shade and to shed 

 rainwater, which occasionally comes down in such quantities as de- 

 cidedly to freshen the upper strata of water, are strongly to be 

 recommended. 



RESULTS. 



CRITERIA OF EFFICIENCY. 



As was stated at the outset, this series of experiments and opera- 

 tions was undertaken in the conviction that the paramount problem 

 of lobster culture was to raise the larvse to the fourth or lobsterling 

 stage. It has been constantly borne in mind that a method of doing 

 this to be practical must be able to produce large quantities and 

 without too great expense either for the cost of the plant or for 

 operation. Further criteria of efficiency are, first, the proportion of 



