1894.] on Embryonic Fission in Lichenopora. 191 



part which I have termed the suspensor corresponding with the inner 

 layer of the bud, and the outer investment with its outer layer. 

 Although this interpretation would make the agreement between 

 Lichenopora and the Phylactolaemata closer than would otherwise be 

 the case, I have not succeeded in showing that the arrangement has 

 really the morphological value of a polypide-bud. 



The polypide now begins to pass into the condition of a new 

 "brown body," with which the old "brown body" fuses. The 

 embryo, with its investments, hangs down into the zoceciurn from the 

 wall of the " brown body," which has meanwhile moved up the 

 zocecium to the neighbourhood of the orifice. In this position it 

 remains during the later stages, becoming much complicated by the 

 processes which succeed. 



The suspensor ceases to be sharply denned as such, its cells merging 

 with those which surround the " brown body " and the embryo. The 

 latter comes to lie close to the " brown body ;" and after a large 

 increase in the number of its nuclei, begins to undergo fission. But 

 whilst in Crisia the primary embryo remains throughout in the con- 

 dition of a coherent mass of cells, which buds off successive embryos 

 into the ovicell, that of Lichenopora early divides up into a consider- 

 able number of irregular pieces, which ultimately give rise to the 

 secondary embryo. In the earlier stages of the process it is easy to 

 show that the pieces are continuous with one another, or that, from 

 their position and structure, they have recently been separated from 

 one another. In older ovi cells it may be difficult to demonstrate the 

 existence of the process of fission, since the number of embryos is 

 increased, to a considerable extent at least, by the binary division of 

 small masses of cells which have all the appearance of young 

 embryos. The details of the fission are, in fact, more similar to those 

 which occur in the fission of the " Urknospen " of certain Tunicata 

 (Doliolum* &c.) than to those which occur in Orisia. 



After the first brood of larvae are hatched the colony may develop 

 new primary embryos at several points in the ovicell. These form 

 the starting points for the development of a fresh brood of larvaa. 

 Thus, early stages in the embryonic development may be found, not 

 only in the youngest colonies, but also in the largest, fully-formed 

 colonies. These latter differ from the young colonies in containing 

 the set of cavities constituting the original ovicell. The primary 

 embryos of the second generation may readily be recognised in 

 sections by means of the characteristic "brown body," to which the 

 follicle containing the embryo is attached. Their earliest stages have 

 not so far been traced ; but the later stages, in which fission is com- 

 mencing, are, in all important points, identical with those of the 

 first generation. 

 * Uljanin (B.) , ' Fauna und Flora G. von Neapel,' X Monogr., 1884, pp. 108 et seq. 



