500 SUMMABY OF CURRENT RESEARCHES RELATING TO 



C. concretum, have been cTistinguislied. The organism forms tubular, 

 chitinous zooecia enveloped in common aggregations of sand ; the poly- 

 pides are provided with a muscular gizzard containing two horny teeth. 

 The chief difficulties in the way of the study of the soft tissues consist 

 in the very minute size of the individual polypides, and in the difficulty 

 experienced in separating them from the mass of sand-grains in which 

 they are enveloped and to which the zooecia firmly adhere. 



The coencecium is dichotomously branched and the branches come oflF 

 in several planes ; it consists primarily of a slender chitinous tube ; the 

 whole is divisible into what may be termed nodes and internodes ; the 

 former are dense aggregations of grains of sand firmly held together by 

 the chitinous zooecia, while the latter are longer or shorter, slender, 

 chitinous tubes connecting the nodes together. It is to be especially 

 noted that the tubular internodes are not continuous through the 

 substance of the sandy nodes, but each, on entering the sandy mass, 

 breaks up into a kind of rete mirabile, formed chiefly of the delicate 

 tubular zooecia. The zooecia are very delicate, and it is possible that, 

 in Cryptozoon, as in those horny sponges which take on an arenaceous 

 habit, the chitinous portion of the skeleton is actually reduced in con- 

 sequence of the addition of the sand, which may be considered as 

 supplementing, and, possibly, to a certain extent replacing the chitin. 

 The wall of each internode appears in oj)tical longitudinal section to be 

 clothed internally with a deeply staining epithelium, the cells of which 

 secrete the chitinous wall of the tube ; this lining is, no doubt, a direct 

 continuation of the coelomic epithelium of the polypides, and appears to 

 be the only organic connection between the different members of the 

 colony. 



So much of the anatomy of the polypide as could be made out is 

 described. The epithelium of the tentacles does not present the same 

 character over the whole surface ; on the inturned face of each tentacle 

 there are two parallel longitudinal rows of small, columnar cells, each 

 of which contains a relatively large, deeply staining nucleus. The cilia 

 on the tentacle are nearly as long as the tentacle is thick, and they 

 always move in a perfectly definite and regular manner. The alimentary 

 canal is very complex, and five distinct parts — pharynx, oesophagus, 

 gizzard, stomach, and intestine — can be recognized in it. 



The gizzard is globular in shape, and has thick muscular walls, con- 

 sisting mainly of a stout circular band of muscles oval in section, and 

 composed of a great number of delicate fibres, surrounding two relatively 

 large chitinous teeth. These last are squarish in shape, and flattened. 

 The stomach is very large, elongated and saccular, and is differentiated by 

 the character of its lining membrane into two totally distinct regions — 

 an upper, non-digestive, and a lower, digestive portion. The eutire ali- 

 mentary canal is clothed externally by a delicate, closely-fitting, flattened 

 epithelium, the nuclei of which are plainly discernible over the greater 

 part of its surface. The muscular system is well developed. 



The author remarks that it is interesting to find a Polyzoon acquiring 

 a habit with which we are already familiar in other groups, such as 

 Foraminifera, Sponges, and Annelids. The genus is obviously closely 

 allied to BowerhanJcia, from which it differs most markedly in the habit 

 of agglomerating particles of sand on to the zooecia. In conclusion, the 

 distinctive characters of the new species are briefly enumerated. 



