626 THE FEESH-WATEE SHEIMP, OE FEESH-WATEE SCIIEW. 



common medusae. It will occasionally leave tins curious residence, and return to it at 

 will. It is about half an inch in length, has the two first pairs of feet shortest, tipped with 

 a claw, and has 'the three last pairs of legs longer than the others. The name of this 

 crustacean is Metoecus medusarum. Mr. Spence Bate separates all these parasitic animals 

 into a distinct family, under the name of Phronimadae. All the members of this family 

 have the mandibles very large, some of the legs prehensile and oddly formed, and the head 

 of enormous comparative size. Some of them attach themselves to fishes, and others to 

 medusae. 



FIGS. C and D represent another strangely formed and closely allied crustacean, whose 

 habits are however very imperfectly known, though it is presumed that they resemble those 

 of the hermit-screw and its kin. In this genus, the head, though large, is not of such 

 enormous comparative dimensions as in Phronima, and is rather squared in form. The 

 strange and grasping legs may be seen by reference to the illustration, some of those 

 members possessing great muscular development, and being armed at their extremities 

 with formidable claws, the moveable joint bending over at right angles. 



FIGS. E and F represent a small, but very remarkable crustacean, one of the few which 

 really construct a home for themselves. The close resemblance between this creature and 

 the well-known caddis-worm cannot but strike an observer. All the animals belonging to 

 this genus inhabit a case which they are able to carry about with them. In spite of the 

 awkwardness of such an appendage, the CADDIS-SHEIMP passes along at a brisk pace, 

 moving by means of the two pairs of long antennas, which not only look like feet, but are 

 used for locomotion. The real feet are kept within the tube, with the exception of the 

 two front pairs, which are almost wholly used for catching prey and feeding itself. 



Some persons imagine that the tube of this creature is not of home manufacture, but 

 is the deserted residence of some annelid. There is, however, no reason why a crustacean, 

 which is much higher in the scale of creation, should not make as good a tube. The 

 material of which these tubes are made resembles rough leather or papier-mache, and 

 greyish brown in colour, and very tough. They are very small, in some species being not 

 more than the sixteenth of an inch in length, and proportionately small in diameter. 

 Sometimes the tubes are set so thickly upon the plant as to conceal its surface from view. 

 They are set without the least order, and look as if they had been simply flung upon the 

 sea- weed to which they adhere. The common carrageen (Chondus crispus}, from which the 

 well-known Irish moss is made, is the plant that is most favoured by their presence. 

 When taken out of its cell, the little animal is not unlike a sand-hopper, except that the 

 two pairs of antennas are enormously developed, and the first few pairs of legs are furnished 

 with small claws. 



The generic name Cerapus is taken from the Greek, and is very appropriate, signifying 

 " horn-footed." These strange antennae are continually flung forward, grasping at every- 

 thing that comes within their reach, and reminding the observer most forcibly of the 

 peculiar actions of the cirrhipeds or barnacles. The Caddis-shrimp does not love the very 

 shallow waters, and, except by use of the dredge, cannot be obtained but at the very 

 low tides of March and September, those precious days so invaluable to the practical 

 naturalist, where he finds laid out before him large tracts of the ocean-bed that, except 

 for a few days, at intervals of six months, remain covered with water, and hide their 

 treasures from all eyes. 



THE central upper figure in the next illustration represents the common FRESH-WATER 

 SHRIMP, or FRESH-WATER SCREW. 



In common with the other Screws, this creature derives its name from its movements 

 when taken from the water and laid upon the ground. Not being able to stand upright 

 upon its feeble legs, it is forced to lie on its side, so that the perpetual kicking of its 

 legs only forces it round in a screw-like fashion, similar to the conduct of the marine 

 screw-shrimp when laid on the sand. 



The Fresh-water Shrimp is extremely plentiful in every stream, and may be seen in 

 great numbers even in the little rivulets that conduct the water from fields. They lurk 



