ALLMAN. — USE OF THE TOWING NET. 56 



seas these low forms of vegetable life abound to such an extent 

 as to discolour the water over very wide areas, and they not 

 unfrequently seriously interfere with the work of the towing 

 net by rendering the washings of the net so turbid as to hide the 

 small animals taken at the same time, while the rapid decom- 

 position of their soft parts speedily vitiates the water and destroys 

 such animals as have been allowed to remain with them. 



To preserve them the washings of the net should be thrown on 

 a filter in order to get rid of the superfluous water, and the matter 

 which remains should while still moist be transferred to glass 

 tubes containing spirit. 



Protozoa. 



Among this lowest group of the animal kingdom the collector 

 should be on the look-out for Radiolarice and ForaminifercB. 

 Though the hard siliceous cases and framework of the Radiolarise 

 and the calcareous shells of the Foraminiferse will usually retain 

 their forms after the destruction of the soft parts, it is far better 

 to transfer to the spirit the whole organism at once by means 

 of the dip tube. Other microscopic Protozoa, such as Noctiluca 

 and Peridinium, as well as the true ciliate Infusoria, ought also 

 to be watched for. Among these last are the Dictyocystidce, 

 a group of pelagic Infusoria having a close resemblance to 

 certain Radiolariae by their elegant siliceous bell-shaped shells 

 perforated in the manner of lattice- work. In most cases, how- 

 ever, these microscopic organisms are so minute as to render 

 impracticable the separation and transference to spirit of any 

 great quantities of them. We must then be contented with 

 putting up such as can be obtained, on microscope slides or in 

 cells, a process, however, which takes time and labour, and needs 

 some practice in the art of microscopic mounting. 



Ccelenterata, 



It is in this group that some of the most abundant and im- 

 portant results follow the use of the towing net. 



Among the most striking and interesting inhabitants of the 

 surface zone of the sea in all latitudes are the Hydroid MeduscB, 

 clear gelatinous, more or less bell-shaped or umbrella-shaped 

 organisms, which mostly originating as buds from plant-like 

 hydroids (or zoophytes) fixed to the sea bottom, free themselves 

 after a time from their supporting stems, and spend the rest of 

 their lives in a state of activity at the surface, where they swim 

 by the expansion and contraction of their gelatinous bells. When 

 possible, drawings ought to be made of these beautiful animals, 

 for no means have yet been discovered of preserving their forms 

 after death with anything like satisfactory results. Many, how- 

 ever, may be fairly preserved by placing them in methylated 

 spirit; and as this seems to be the best method we possess 

 of preserving their zoological characters, it should never be 

 neglected. 



Nearly allied to the Hydroid Medusas, and with very similar 

 habits, are the Siphonophora, These usually form long garland- 



