the neighbourhood of Edinburgh Cypris gibba is plentiful, some- 

 times gregarious almost to the exclusion of all others, whereas, on 

 the west coast, it has been my experience to find that species but 

 sparingly distributed. 



Goniocypris mitra and Cypris punctillata are common to the east 

 of Scotland and the fen districts of England, but are not yet 

 recorded in the West of Scotland. Still, it is true that, on a com- 

 parison of localities one with another, so far as the results have 

 been brought out, there is less difference existing between stations 

 widely apart than might have been expected. The means of dis- 

 tribution do not seem to depend so much on the facilities of 

 transport as on the conditions of locality. Ostracoda may be 

 abundant in ditches and absent in the lochs and tarns that receive 

 their waters. Examples of this are so common that they must be 

 familiar to every one who has paid any attention to the subject. 



The Ostracoda in this list, which may be considered to belong 

 exclusively to brackish water, but never by choice to be purely 

 marine, are Cypris salina, Gypridopsis aculeata, Cytheridea torosa, 

 and its variety teres. The latter species and variety, although more 

 estuarine, may be placed in the same category. Cypris incongruens 

 and Cypridopsis obesa are frequently found in brackish water, but 

 as frequently in purely fresh water. Many other species are occa- 

 sionally met with in water more or less brackish, as in ponds a little 

 above high-water mark, subject to the spray of the sea during high 

 tides and storms, but chiefly in fresh water quite beyond the reach 

 of marine influences. A group of small ponds lying close together 

 along the south-west shore of the island of Cumbrae, and apparently 

 subject to an equal amount of spray, may here be referred to. 

 These ponds are mostly within a few yards of each other, and seem 

 to be exposed to similar conditions, yet their microscopic fauna are 

 found, when compared, to differ widely. A list of Ostracoda found 

 in ten of these sub-brackish patches of water will best show the 

 great number of reputed fresh- water species associated with those 

 which constantly affect brackish water, and also the diversity in the 

 numbers and grouping of species existing between one pond and 

 another. This mixture of fresh and brackish-water species is all the 

 more remarkable, as none of these ponds communicate with the 

 others, nor with any fresh-water stream. All of them, as stated, 

 are within a short distance of each other, only a little above high- 

 water mark, and subject to the spray of the sea. The effect of this 



