1894.] on Embryonic Fission in Lichenopora. 189 



be compared with a funnel with, a basa'l angle of nearly 180, passing 

 off into a short stalk, which is curved round so as to lie between the 

 base of the funnel and its attachment. 



The funnel is composed of a multitude of closely packed pyramidal 

 tubes, whose wider ends open at the surface in the manner of the 

 cells of a honey-comb. These are continuously formed at the margin 

 of the colony, where fresh tubes are constantly cut off, simultaneously 

 with the extension of the margin, by the upgrowth of calcareous septa. 

 The body-cavity is here closed in on the upper side by an uncalcified 

 body- wall. The new septa are developed at the growing edge in such 

 a way that two kinds of tubes are formed. These give rise respec- 

 tively to the zocecia and to the ovicell. The zocecia all reach the 

 base of the colony, where they are in close contact with one another. 

 In growing upwards they diverge, so that a set of pyramidal spaces, 

 narrow below and widening above, originate between them. These 

 spaces, from which the ovicell is developed, acquire complete calca- 

 reous walls, their roof remaining at first membranous. Each con- 

 tains a part of the body-cavity, cut off from the growing edge of the 

 colony, and the spaces may accordingly be compared with zocecia, in 

 which, however, no polypide-buds are formed. 



The membranous roof of these interzocecial spaces becomes calci- 

 fied, thus forming a "crust" which extends horizontally between 

 adjacent zocecia. The side walls of the spaces then break down, and 

 a large continuous cavity thus results. This cavity, the ovicell, lies 

 superficial to the bases of the zocecia, some of which pass through it 

 as free columns which project beyond its roof. The ovicell later 

 acquires one or more trumpet- shaped openings to the exterior. 



The mature ovicell contains several hundred larvae in various 

 stages of development. These, constituting the first brood, have all 

 been derived from the primary embryo which normally develops in 

 one of the two zocecia first formed from the primary zocecium. 



The beginning of the developmental processes was found in a 

 colony consisting of three zocecia only. Each of these contained a 

 " brown body " and a mature polypide. The polypide of the primary 

 zocecium, like that of one of the two secondary zocecia, possessed a 

 testis, attached to the lower end of its alimentary canal. That of 

 the remaining zocecium had an egg in the corresponding position. 



A precisely similar egg was found, in one or two young colonies, in 

 a polypide-bud, where, from its position, it had probably been de- 

 veloped from the outer (mesodermic) layer of the bud. Eggs are not 

 necessarily confined to a single polypide in the colony, but in a con- 

 dition in which they can be recognised as eggs, they do not appear to 

 be developed in most cases except in the polypide destined to give 

 rise to a primary embryo. The testis, on the contrary, may be re- 

 garded as a normal possession of every polypide. It usually gives 



