Stephens — The Fresh-ivatcr Sponges of Ireland. 21'i 



discovery in Ireland of Ilctcrumci/cnia liijdcri, luid, as was supijosed at Llie 

 time, of two otliev species witli a similar distribution. We find, therefore, 

 dui'ing the next few years that the ciiief references to Irish fresh-water 

 sponges were made in connexion with the questinii <il' their di.strihntion. 

 Dr. Scharff in several of his books and papers (^35, 36, 37) and i'rofessor 

 Carpenter (13) cite the distribxition of these fresh-water sponges, along with 

 that of certain other invertebrates and plant.s, in su[iport of the theory of the 

 existence of a former land-bridge between North America and Europe. 

 Later on, when two of the three sponges were found in India, the species 

 were naturally quoted as good examples of discontinuous distribution (3). 



Two or three short notices giving additional Irish localities for some of 

 the species bring us up to the commencement of the Clai'e Island Survey, 

 when for the first time in this country a systematic search for fresh-water 

 sponges was undertaken in a definite area, namely, in western Mayo and in 

 the adjacent islands off the coast. In point of view of mere number of species, 

 the result of the Survey was disappointing, only Si)onfjilla fvagilis being 

 added to the list, while Tiibclla peniisylccmica and Ephydatia crateriformis 

 had to be deleted. The chief points brought forward in the report may be 

 briefly referred to. First, that sponges were few-er in number of species, and 

 grew as a rule with less luxuriance in lakes on the limestone than in the 

 fresh waters of the non-calcareous areas ; and, secondly, that Hderomeyema 

 Byderi was absent from the fresh waters of the limestone areas. It is 

 satisfactory to state that these observations have been confirmed by work 

 done subsequently in many parts of Ireland. Thirdly, it was found that 

 Meteromeyenia Byderi assumes different forms in lakes and ri\ers, which 

 forms are closely analogous to the varieties of the species described from 

 North America. 



A few short notices giving additional localities for some of the species 

 bring the list of references to Irish fresh-water sponges to a close. 



The material on which the present paper is based has been collected for 

 the most part by the present writer in different parts of Ireland during the 

 past ten years. Many areas have been very thoroughly searched, but several 

 parts of the country have been left almost untouched owing to various 

 reasons — for instance, two or three unusually wet seasons which delayed the 

 work, and, during ihe last few years, the increasing difficulties of travelling 

 in Ireland for the purpose of collecting natural history specimens. In 

 particular, the midlands have been neglected, and further work in parts of 

 the north and in the south would add to our knowledge of the distribution of 

 the various species. 



