INVERTEBUATA, CRYPTOGAMIA, MICROSCOPY, ETC. 691 



the large, thick-slicllcd species; those with fragile and delicate shells, 

 that is to say the most luimci'ous and beautiful, can only live and 

 develop properly on muddy bottoms, or where the sand is fine and 

 somewhat slimy, and it is necessary therefore to investigate such 

 deposits also. For this purpose, some of the following indications 

 may be followed according to the locality. 



Collect at low water (cither with the hand or a small dredge) the 

 superficial portion of the mud or slimy sand found in ports or the 

 mouths of rivers, or higher up in their course if the water is salt. 

 The glutinous coating, generally green or brownish, which covers tho 

 mud or slimy sand in quiet places often gives excellent results. The 

 thick black rnud beneath is less rich in Foraminifcra than the upper 

 portions. 



It is also useful to explore tho large pools which remain at low 

 water, either on the shore when the sand is not too coarse, or in the 

 estuaries, or even the cavities often met with among the rocks or at 

 the foot of clifls. It must be remembered that the most favourable 

 spots are always those which are covered with very fine or slimy sand. 

 Sediments which are coarser but rich in fine debris, are also 

 favourable. 



Whitish zones are sometimes seen on the margins of pools left at 

 low tide, composed of little heaps accumulated in the numberless 

 ridges produced in the sand by tlio retreating water. These whitish 

 heaps consist of small organic debris, spiculro of sponges, si)ines of 

 echinoderms, fragments of shells, &c., often mixed with a quantity of 

 Foraminifcra, of which a great many can be collected by a spoon. 



By means of a simple magnifier the presence of living Foraminifcra 

 can be established on the spot. If, for example, some of the deposit is 

 examined in a shallow vessel (such as the cover of a tin box) and 

 under a small quantity of water, the Foraminifcra will bo readily 

 recognized as small coloured points of red, rose, or yellow — tints 

 which are given to the thin shell of many species by the colour of tlie 

 sarcode within. 



Tlie places whei'o the water is relatively quiet arc the only really 

 fav«)urablc ones for finding Foraminifcra. 13redgings from a dei)th of 

 from 8 to 10 metres (when the water at tho bottom is little moved, 

 however rougli it may be on the surface), always give good results, 

 unless tlic bottom consists of })urely quartz deposit or gravel, as is tlie 

 case in regions subjected to rapid submarine currents, as in the Straits 

 of Dover. Tho interest of tho collecti(ms increases in proportion to 

 the depth at which tlicy liave been made. 



For the benefit of those who liavo not dredges at their command, 

 it may be mentioned that the mud brought on board by tho anchors 

 of ships, or the detritus on tho nets of fishermen, furnish sj)ocies which 

 are not found on the coast. 



Foraminifcra may also be found in tho contents of tho stomachs of 

 fishes, molluscs, crustacea, actinisp, mednsjo, salpio, i^'c. 



Certain species of Annelida, Tf rebel Uv. for instance, form a pro- 

 tecting sheath wliich often contains Foraminifcra not found on the shore. 



'J'ho sand and slinio oi salt marshes in ncrioilical connnunieation 



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