6 INTEODUCT10N. 



characters by which we can positively say, whether a given fossil 

 be a- Bryozoan or not. There are some large groups of Palaeozoic 

 fossils which may belong either to the Bryozoa, Actinozoa, or 

 Hydrozoa. There are also numerous Jurassic fossils whose 

 affinities have loag been matter of dispute. Nevertheless, by 

 means of detailed investigation of some existing allied animals, 

 and by microscopic investigation of the fossils, it is possible to 

 settle the probable affinities of these doubtful forms. Hence 

 certain fossils, which have been often assigned to the Corals, are 

 included in the present Catalogue as Bryozoa ; and others, such as 

 the genera Acanthopora, Neuropora, and Chrysaora, which have 

 been previously considered to be Bryozoa, are excluded as 

 Hydrozoa. 



2. THE AFFINITIES OF THE BRYOZOA. 



Unlike most animals we cannot refer the Bryozoa to any one 

 of the eight phyla, or great divisions of the animal kingdom. 

 Although their anatomical structure is well known, their 

 systematic position is uncertain. When first studied they were 

 regarded as plants, which was the orthodox view until the middle 

 of the last century. Peysonnel, indeed, had discovered sufficient 

 to show the erroneous nature of this conclusion; 1 but his arguments 

 were unheeded owing to the opposition of Reaumur, who reported 

 Peysonnel's observations to the Academie des Sciences in 1727. It 

 was not till 1742 that Jussieu 2 figured the creatures that form the 

 skeletons, and conclusively proved their animal nature. But even 

 then this theory was not accepted. Baster, 3 in 1760, explained 

 the polypi as only parasites on the surfaces of aquatic plants ; and 

 Linneus, 4 even in his latest work, separated the zoophytes from 

 the corals, and expressed his conviction that " sunt enim stipites 



1 De Reaumur. Observations sur la formation du Corail et des autres pro- 

 ductions appellees Plantes pierreuses : Mem. Acad. roy. Sci. 1727, pp. 276-7. 



2 Bernard de Jussieu. Examen de quelques productions marines qui ont ete 

 mises an nombre des Plantes, et qui sont 1'ouvrage d'une sort d'Insectes de iner : 

 Mem. Acad. roy. Sci. 1742, pp. 290-302, pis. ix., x. 



3 Jobus Basterus. Opuscula subseciva Harlem, t. i. lib. 2, 1760, p. 61. 



4 Systema Naturae, ed. 12, t. i. pars 2, 1767, p. 1287. 



