Salt Marshes and their Inhabitants. . 31 



than in any other genus. The segments of the body and their 

 corresponding appendages maybe seen very clearly, there being- 

 little or nothing of that pressing together and consolidation of 

 several parts which is so constantly exhibited in both the higher 

 andlower orders.* We should scarcely expect to find in an animal 

 of this grade much development of maternal instinct, and yet 

 some observers have noticed such manifestations. The ova of 

 Crustacea are mostly attached in a considerable mass, to the 

 abdominal or false feet of the female. In Gammarus (and 

 in some other genera) they remain in situ for some time after 

 having taken on the crustacean form, and even when able to 

 swim freely, they will often hover round the parent in a little 

 cloud, and when any danger threatens, again seek refuge 

 amongst her legs. G. locusta is easily recognized by three 

 conspicuous red spots on each side of the body, upon the ab- 

 dominal segments. It is a very common species, but is almost 

 confined to the upper portion of the littoral zone, haunting chiefly 

 shallow tidal pools, and especially those heaps of decaying sea- 

 weed which strew the shore between tide marks. In such 

 situations it may often be found in countless numbers. Its 

 range extends up tidal rivers to the utmost verge of brackish 

 water, and it may even be met with in ditches to which salt 

 water gains access only once or twice in the year. 



A species of Sphseroma (S. rugicauda ?) is one of the most 

 generally distributed Crustacea of brackish water, and is, 

 indeed, almost the only representative of the Isopods met with 

 in such places. The species of this and some allied genera 

 (Armadillidium, Porcellio, etc.) have the curious habit of rolling 

 themselves into a little ball when handled, remaining motionless 

 while in this position. The terrestrial species have obtained 

 for this reason the trivial name of " pill beetles." It is remark- 

 able that some of these animals are able to live indifferently, 

 either 1 in the deep sea or on dry ground removed from any 

 marine influence. Thus we have taken Porcellio scaber abun- 

 dantly on dry sandy hedge-banks, and likewise from the nets 

 of trawlers in fifteen fathoms water. Such a fact is very 

 curious and suggestive, quite as much so as many of the 

 hypothetical cases put by Mr. Darwin in his work on the 

 " Origin of Species," and which have been so much ridiculed 

 by the opponents of his theory. 



Among the Entomostraca of salt-marshes we find some very 

 interesting species. One of the bivalved forms {Cyprideis torosa) 

 was first described by Professor T. Rupert Jones, as a fossil 

 species occurring in the Tertiary strata. Mr. Jones likewise 

 took it living in ditches near Gravesend, and it has since been 



* For an account of the structure of the skeleton of a typical Crustacean, vide 

 Intellectual Obseeyeb, toI. iii., page 38. 



