ALLMAN. — USE OF THE TOWING NET. 57 



Vermes. 



Among the Vermes (Sea Worms, &c.), we have some remark- 

 able pelagic free -SAvimming forms which frequent the uppermost 

 zone of the sea. 



The curious Sagitta, a little clear crystalline stylette-like body 

 from half an inch to an inch in length with a delicate quadrilateral 

 tail -fin, and moving by a succession of rapid jerks, is sometimes very 

 abundant in the British seas, and would probably be found further 

 north. So also the beautiful Tomopteris, a little animal of the 

 purest transparency, attaining a length of about an inch and pro- 

 vided with a series of transparent double paddle-like fins which 

 run down each side of the body, is another pelagic form of the 

 Worms which ought to be met with in high 1 atitudes. Both these 

 animals will be best preserved in spirit. 



A great many of the Sea Worms, however sedentary they may 

 be in their adult stages, are in their larval condition free-swimming 

 pelagic forms. They are full of interest in the light they throw 

 upon the phenomena of development, and on the affinities of dis- 

 tant groups of the animal kingdom. They should, therefore, be 

 always carefully noted, removed by the aid of the dip tube from 

 the washings of the net, and preserved as far as possible by 

 immersion in spirit. 



Arthropoda. 



Among the invertebrate life which abounds in Arctic seas, and 

 which from the concurrent testimony of Arctic voyagers constitute 

 a characteristic feature of their fauna will be found the Amphipo- 

 dous Crustacea. These are small active animals, most familiarly 

 known to us by the " sand hoppers " of our own shores. In Arctic 

 regions they are often attracted in countless multitudes by frag- 

 ments of offal thrown ' into the sea. To such an extent do thej^ 

 abound there that the carcass of a seal has been in a few hours 

 reduced by them to the condition of a clean skeleton. They frequent 

 various depths from the surface downwards, and may be all well 

 preserved in spirit. 



Among the Isopod Crustacea [Idotea^ &c.), we also find active 

 free-swimming species which frequent the surface zone of the sea 

 and are constantly captured in the towing net. They may be pre- 

 served like the amphipoda in spirit. 



Minute Entomostracous Crustacea, especially those belonging to 

 'the group of the Copepoda, are often captured in amazing quanti- 

 ties in the towing net. As with other microscopic forms the 

 attempt to separate them from the washings of the net with the 

 view of preserving them is troublesome and difficult. If how- 

 ever the collector has an abundant stock of patience he may here 

 use his dip tube and phials of spirit with advantage. At all 

 events other animals which it may be desirable to preserve for 

 any length of time in a living state should never be left along 

 with these little Crustacea when they are contained in the jars rn 

 any considerable quantity, for the Entomostraca rapidly decom- 

 pose and render the water unfit for other forms of life. 



3G122. e 



