COLLECTION OF AQUATIC OBJECTS. 23? 



is well that the bottles should be fitted into rases, to avoid the 

 risk of breakage. When Animalcules are being collected, the 

 bottles should not be above two-thirds filled, so that adequate 

 air-space may be left. — Whilst engaged in the search for Micro- 

 scopic objects, it is desirable for the Collector to possess a means 

 of at once recognizing the forms which he may gather, where this 

 is possible, in order that he may decide whether the ' gathering ' 

 is, or is not, worth preserving ; for this purpose either a powerful 

 'Coddington' or 'Stanhope' lens (§ 19), a Gairdner's Doublet 

 Microscope (§ 35), a Tomkins's Diatom-finder (§ 35, note), a Beale's 

 Pocket Microscope (§ 56), or the Travelling Microscope of Messrs. 

 Baker or of Messrs. Murray and Heath (§ 58), will be found most 

 useful, according to the class of objects of which the Collector is in 

 search. The former will answer very well for Zoophytes and the 

 larger Diatomaceae ; but the latter will be needed for Desmidiacea?, 

 the smaller Diatomaceaa, and Animalcules. 



177. The same general method is to be followed in the collection 

 of such marine forms of Vegetable and Animal life, as inhabit the 

 neighbourhood of the shore, and can be reached by the Pond-stick. 

 But there are many which need to be brought up from the bottom 

 by means of the Dredge ; and many others which swim freely 

 through the waters of the ocean, and are only to be captured by the 

 Tow-Net. As the former is part of the ordinary equipment of every 

 Marine Naturalist, whether he concern himself with the Microscope 

 or not, the mode of using it need not be here described ; but the 

 use of the latter for the purposes of the Microscopist requires special 

 management. The net should be of fine muslin, firmly sewn to a 

 ring of strong wire about 10 or 12 inches in diameter. This may 

 be either fastened by a pair of strings to the stern of a boat, so as 

 to tow behind it, or it may be fixed to a Stick so held in the hand 

 as to project from the side of the boat. In either case the net 

 should be taken-in from time to time, and held up to allow the 

 water it contains to drain through it ; and should then be turned 

 inside-out and moved about in a bucket of water carried in the 

 boat, so that any minute organisms adhering to it may be washed 

 off before it is again immersed. It is by this simple method that 

 Marine Animalcules, the living forms of Polycystina, the smaller 

 Medusoids (with their allies, Beroe and Cydippe), Noctiluca, the 

 free-swimming larvae of Ecidnodermata, some of the most curious 

 of the Tunicata, the larvae of Mollusca, Turbellaria, said Annelida, 

 some curious adult forms of these classes, Entomostraca, and the 

 larva? of higher Crustacea, are obtained by the Naturalist ; and 

 the great increase in our knowledge of these forms which has been 

 gained within recent years, is mainly due to the assiduous use 

 which has been made of it by quabfied observers. — It is important 

 to bear in mind that for the collection of all the more delicate of 

 the organisms just named (such, for instance, as Echinodcrui 

 larva;), it is essential that the boat should be rowed so slowly that 



