INVERVEBRATE ANIMALS OF VINEYARD SOUND, ETC. 317 



terior legs, and exteudiug tlie body out at an angle, with the long, rough 

 front legs stretched out in various directions. While in these attitudes 

 and at rest they often closely resemble the branches of the hydroids 

 and alga^ among- which they live, especially as they also imitate them in 

 colors, for all these species are variable in color, being generallv "rav 

 with darker specks, when living among- hydroids, but often bright red 

 when living among red alga^. This habit of holding themselves stiffly 

 in such peculiar positions recalls the similar habits of many insects, es- 

 pecially some of the Orthoptera and the larvtii of the geometrid moths, 

 and they also recall the larvie, just named, by their singular mode of 

 climbing- actively about among the branches of the hydroids and algip, 

 for they bend the slender body into a loop, bring the hind legs up to the 

 front ones, and taking- hold with them stretch the body forward again, 

 just like those larvie, though their legs are long and slender and differ 

 widely in structure. These little creatures are very pugnacious and are 

 always ready to light each other when they meet, or to repel any in- 

 truder similar in size to themselves. Their large claws are well adapted 

 for such purposes. 



The marine worms or Annelids are very numerous under the rocks be- 

 tween tides, and concealed beneath the surface of the gravel and mud 

 that accumulates between and beneath the stones and in crevices. 

 Many kinds also live in the pools, lurking- among the roots of the alg*, 

 burrowing- in the bottom, or building- tubes of their own in more ex- 

 posed situations. Many of these annelids are very beautiful in form 

 and brilliant in color when living, while most of them have curious hab- 

 its and marvelous structures. Several species are of large size, grow- 

 ing to the length of one or two feet. Some are carnivorous, devouring 

 other worms and any other small creatures that the}' can kill by their pow- 

 erful weapons; others are vegetarians ; but many are mud-eaters, swal- 

 lowing the mud and fine sand in great quantities, for the sake of the 

 animal and vegetable organisms that always exist in it, as is the case 

 with clams and most of the bivalve shells, and many other kinds of 

 marine animals. 



All these Annelids are greedily devoured by most kinds of marine fishes, 

 whenever they can get at them, and, since many of the annelids leave 

 their burrows in the night to swim at the surface, or do this constantly 

 at the breeding season, they make an important element in the diet of 

 many fishes besides those that constantly root for them in the mud and 

 gravel, like the tautog, scup, haddock, &c. The young of nearly all 

 the annelids also swim free in the water for a considerable time, and 

 in this state are doubtless devoured in immense numbers by all sorts of 

 young and small fishes. 



One of the largest and most common Annelids found under rocks, 

 burrowing in the sand and gravel, is the Nereis virens, (Plate XI, figs. 

 47-50.) It lives both at low-water mark and at a considerable distance 

 farther up. It grows to the length of eighteen inches or more, and is 



