40 DISCOPHOR^. Part III. 



shape of the veil is very peculiar, not so much in the lateral ovate outlines as in 

 the disijosition of its upper and lower surfaces ; the whole thickness is gradually 

 depressed from the edge to the centre {Fifj. 9 i^) : but the hollow is deepest near 

 the base. In a foreshortened view {Fig. 4 A), especially when the veil is turned 

 inwaixl toward the proboscis, this hollow is very marked. The extent of the veil 

 is about half the length of the oculiferous lobes. The proboscis has lost its rounded 

 corners, which now appear as if cut straight across {^Fig. 4 «^), the meaning of 

 which will be seen in the next phase. Already the lips (a) have become thin and 

 transparent, ajiproximating the trumpet-mouth foi-m which they soon after adopt. 

 The four columnar supports or buttresses (a^), so characteristic in the proboscis of 

 the adult (PI. VII. Fig. 5), are here already very marked; they stand opposite four 

 of the eyes, and extend their several bases as far as the borders (PI. XP. Fig. 4 J^) 

 of the digestive cavity. 



In the last phase we pointed out the completion of the circular canal; and 

 now we find already the radiating canals are branching. The process by which 

 this is done is very sim23le. The inner Avails of the upper and lower floors of 

 the disk sejjarate along the line intended for the course of the canal, and thus 

 a channel is formed. At It^ Fig. 4 we have this process going on : the ujaper 

 and lower walls of this projection are sejiarated on the side next the jjerijihery, 

 and a more direct passage to the canal of the oculiferous lobes is made, whilst 

 an isolated column {P) is left, around which the chymiferous fluid circulates. In 

 this way the circular canal {Fig. 2 c^) w^as formed in the previous stage. In order 

 to make this process clearer to the reader, we refer for a moment to a transverse 

 section of the canals of an older stage {Fig. 13) ; here it will be evident, that, 

 simply by the separation of the two walls at Jc, the two adjacent canals c and e 

 will merge into each other; and this is the way that all the canals are formed 

 in succeeding ages of the ephyra. The breadth of the eight canals {Fig. 4 c^ c^) 

 which lead to the eyes is remarkalile ; and their nearly equilateral triangular outline 

 contrasts strongly with the straight, parallel sides of the eight simjDle canals {e) 

 which go to the margin. We have an instance here, in an incijiient state, of the 

 branching (e^) of a normally simple, straight canal, such as may be seen in an adult 

 specimen (PI. VII. Fig. 5 d). The sexual organs (PI. XP. Fig. 4 g) show signs 

 of advancement merely by the increase in the number and length of the digitate 

 appendages. 



The margin of the disk has begun to be complicated. In the first j^lace, the 

 separation of the outer and inner walls at this point, as observed in the previous 

 phase {Fig. 2 i"^ i^), has resulted in the formation of two marginal lobules {Fig. 3 ^^), 

 one on each side of the single tentacle {i^). The exact relation of these appendages 

 will be better understood by referring to their adult state (PI. VII. Figs. 2, 3, 4 b). 



