THE MOUNT DESERT REGION 81 



environmental influences and represent constant genetic fea- 

 tures. Thus, of all the tangible characters found in sponges 

 the shape, and, usually, the size of the spicules, especially of 

 the microscleres, constitute the best basis for classification. 



Most of the taxonomy of the sponges was done before 

 the development of genetics had broadened our conception of 

 a species and many of the ' literature-species ' will undoubtedly 

 be found after more intensive study to be only local varieties 

 of more widely spread species, especially as many of these 

 species rest upon a few and, in many cases, a single specimen 

 or a 'few fragments.' However, such cannot be avoided until 

 more is known of the limits of variation within single species 

 as exhibited throughout its entire range of distribution. Thus, 

 in the cosmopolitan and w^ell-known Halichondria panicea the 

 size of the spicules varies from 0.2 mm. to 1.0 mm. This 

 indicates that such might be the case in many other species 

 if they were as well studied as H. panicea. However, judging 

 by the descriptions in the literature, very little variation was 

 tolerated by the older workers. Such a variable character 

 as the size of the spicules has been shown to be in one case, 

 was defined within very narrow limits, and many of the 

 'literature species' rest upon this criterion along. H. V. Wil- 

 son has pointed out that as our knowledge of sponges in- 

 creases the number of genera and species known to grade 

 into one another increases. In such cases it is either neces- 

 sary to overhaul the system in use and establish new cate- 

 gories or else define arbitrary limits to genera and species. 

 Due to the author's limited experience and material it has 

 been considered advisable to do the latter and leave the more 

 difficult task of renovating the system to more experienced 

 workers with a greater amount of material at their disposal. 

 There is very little literature of any worth on the sponges 

 of the northeastern coast of America. Lists of the sponges 

 taken in the Gulf of St. Lawrence (Whiteaves), Casco Bay 

 (Kingsley, Verrill), Vineyard Sound and adjacent waters 

 (Verrill, Woods Hole Survey), and Hudson Bay (Lambe) are 

 available, but no descriptions are included and one can only 



