OF THE CRUSTACEA. 177 



friend already mentioned, viz. — the common Shore Crab. The 

 hardy constitution of this species is no doubt the cause of its wide 

 distribution. Besides a range of considerable dimensions outside 

 the limits of our own seas, it occurs on almost every possible 

 variety of coast in this country. It swarms in harbours, muddy 

 estuaries, or busy docks ; it may be seen scuttling along the wet 

 sand at any sea-side resort ; it assumes tints and shades of delicate 

 hue amongst the rich Zostera pools of the Channel Islands, and 

 it lives and attains to a goodly size on the bleak, cold shores of 

 Shetland. If therefore a species be required whose Zooea could 

 stand the strain, I think this would be the best for the purpose. 



And now for the tanks necessary for the " cultivation " of 

 Carcifius mcenas. In Sa'e?ice Gossip for January last, I figured and 

 described a series of small breeding tanks, fitted with reservoirs, 

 so constructed that when one reservoir was discharging its 

 contents into the top tank, the lower tank, having received the 

 overflow, again discharged it into the other, when, by reversing the 

 reservoirs, by a simple mechanical arrangement, the operation 

 was repeated. This, with occasional attention, would cause an 

 almost perpetual flow of water, and in addition to this, a certain 

 quantity of the reserve sea- water would always be in the dark. 

 The advantage of such a series of tanks as these for hatching 

 out Zocea of Crustacea is that the water does not become 

 stagnant, and consequently fatal to its inmates. Of course 

 the ends of the overflow pipes should be covered with the 

 finest wire gauze, and sheets of glass should also be placed on the 

 tanks to exclude dust ; the bottom of each should be covered 

 with well-washed, coarse sand, and the water itself need not be 

 more than from two to six inches in depth. One of the most 

 important items to be remembered is, that these tanks should be 

 placed in a cool north aspect, with little or no direct sunlight. 



Having obtained a female crab, with dark-coloured ova (the 

 dark colour of the ova is a proof of their being near maturity, 

 immature ova being yellow, red, or very pale brown, whereas the 

 mature ova become nearly black as the eye of the Zooea begins to 

 form), place her in one of the tanks, and supply her with a piece 

 of broken flower-pot, or some such object, under which she can 

 crawl, for some Crustaceans are very shy, and shelter should at all 



