1896.] 125 



IRISH FRESHWATER WORMS. 



BY REV. HIIvDKRiC FRIKND, F.I,.S. 



Ali. true worms may be divided into two great classes or 

 groups, based on the relative number of their bristles or setae. 

 If they are very numerous they are known as poljxhsetous 

 worms or Polychaeta ; if few, they are called oligochsetous 

 worms or Oligochaeta. It is true that the rule has exceptions, 

 and some worms belonging to the Oligochaeta have more 

 setae than are to be found in some species belonging to the 

 Polychaeta ; but then there are other considerations. As a rule 

 the worms with many bristles are marine, and being specially 

 adapted for life in the ocean are quite distinct in form from 

 those belonging to the land and fresh water. Hence generally 

 speaking the Oligochaeta are terrestrial, the Polychaeta marine. 

 Of the Polychaeta I shall for the present have nothing to say, 

 further than this, that very rarely the Polychaeta and 

 Oligochaeta meet, as one might expect in estuarine and salt- 

 marsh habitats. The true Oligochaeta again are separable into 

 two very distinct groups, and the order contains the ter- 

 restrial forms and those which are found either in or near 

 fresh water. The terrestrial forms or true earthworms have 

 received considerable notice in these pages, and while we 

 still hope to add a few further species to the Irish list, it may 

 be said roughly that the earthworms of Ireland are well known. 

 Of the limicolous and aquatic species, however, we have here- 

 tofore been in absolute ignorance. They are small, not easily 

 discovered, and when found are very difficult to determine, so 

 that one need not wonder that they have been little studied. 

 Now, however, thanks to the labours of Mr. Beddard, we have 

 a Monograph' which contains much information for the 

 guidance of the student, and it is to be hoped that before long 

 the aquatic worms of Ireland will be as completely understood 

 as the larger species are. 



Thanks to the kindness of my indefatigable correspondent, 

 Mr. Trumbull of Malahide, I have already been able to make 

 a start with the study, and I send a first instalment in order 

 if possible to secure the interest and aid of the large and 

 ready band of co-workers who so generously supplied me with 



^F. :e. Beddard, "Monograph of the OHgochseta." Oxford, 1895. 



