60 ALLMAN.— USE OF THE TOWIISTG NET. 



he may have observed it. On occasions when the luminosity of 

 the sea may be exceptionally intense, or when on the other hand 

 this phenomenon may be exceptionally feeble, the temperature of 

 the sea and the meteorological conditions present should be care- 

 fully noted. 



Times of using the Towing Net. 



The hours during which the towing net may be employed with 

 the best results are various. In the temperate and equatorial seas 

 some of the surface-dwellers remain habitually in the deeper 

 regions during the day, and come to the surface only in the 

 evening and during the night, while others will be found near the 

 surface only in the daytime. In such latitudes the surface-life of 

 the sea is usually found most abundant about sun rise, and again 

 shortly after sunset. In Arctic regions, however, with the very 

 different distribution of light and darkness, the habits of marine 

 animals may be something quite different. These can be learned 

 only by careful observation, and we as yet know little or nothing 

 of them. 



Preserving Liquids. 



In the above directions the only preserving liquid mentioned is 

 alcohol. This is certainly the most generally useful one, and will 

 probably be found the only one practically available in high polar 

 latitudes. It may be used in the form of methylated spirit of the 

 ordinary commercial strength. 



Schulze recommends for the preservation of very small Medusae 

 and other small delicate organisms, that they be placed, while alive, 

 in a watch-glass with sea water, and then rapidly killed by drop- 

 ping into the water a 1 per cent, solution of osmic acid. After 

 lying some minutes in the osmic acid they are to be immersed in 

 pure water, and from this transferred to spirit. 



8. Supplementary Instructions. By Professor Huxley, 



Sec. K.S. 



The authors of the preceding pages have so fully covered the 

 ground of zoological instruction, that I have but few observa- 

 tions to offer. 



It is desirable that no opportunity of seeking for Insecta, Arach- 

 nida, Myriapoda, and Annelida, on land or in fresh water, should 

 be neglected. As in the Swiss glaciers, insects may occur in pools 

 on land ice. Considering how few such specimens are likely to 

 be obtained, it will be well to preserve any that may be found in 

 spirits. The contents of the crops of birds will be worth exami- 

 nation on the chance of finding remains of such animals. Minute 

 fresh-water entomostracous Crustacea and Infusoria are particu- 

 larly worthy of notice and preservation. The latter may be pre 

 served in spirit if previously treated with osmic acid. 



