134 LIFE BY THE SEASHOEE. 



of contrast with the starfishes. While in the latter it is 

 common to find that the arms exceed five in number, in the 

 Ophiuroids this is not the case. As the name brittle-star 

 indicates, the Ophiuroids are generally very fragile, but the 

 somewhat rare starfish Luidia shows that the same fragility 

 may occur in the Asteroids. Indeed, though our British 

 Asteroids and Ophiuroids are sharply marked off from one 

 another, when the groups are considered as a whole their 

 close relation becomes obvious. 



On account of the large amount of lime in the tissues, 

 the starfishes and some of the Ophiuroids make good dry 

 preparations, and are often most easily preserved in this 

 way. In the case of the larger starfish it is desirable to 

 remove some of the water from the tissues before allowing 

 the specimens to dry. This is best accomplished by placing 

 the animal in spirit for twenty-four hours, changing the 

 spirit once during that time. This "dehydrating" process 

 may be conveniently carried out in a pie-dish covered by a 

 plate. Afterwards the starfish should be lifted out and 

 allowed to dry slowly in air ; a well-ventilated outhouse, or, 

 in default of it, a shady window-ledge, is a good situation 

 for the process. The dried specimens should be kept in a 

 cabinet with camphor or some other preservative against the 

 attacks of insects; if they become damp, or show signs of 

 " going wrong " in any way, a repetition of the dehydrating 

 and drying process is often effective. In the case of the 

 brittle-stars, the prime difficulty is usually to obtain a 

 perfect specimen either to dry or to preserve, for the animals 

 usually break up in dying. In some cases at least specimens 

 may be instantly killed without rupture by dropping them 

 suddenly into boiling water, and as death is practically 

 instantaneous, the objection of the apparent cruelty need 

 hardly be entertained apart from the other debated 

 question how much a brainless animal like an Ophiuroid 

 can really "feel." Specimens killed in this way become 

 abnormally brittle after death, and must be handled with 

 extreme caution. 



The next set of Echinoderms is constituted by the sea- 

 urchins, which have this advantage over the brittle-stars 

 that they are more or less familiar to everyone. To study 

 the general characters you should provide yourself with a 



