147 



opens outwards immediately on the distal side of the operculum of the proximal 

 zooecium. These zocEcia, of which several may sometimes occur in succession, are 

 supposed by Repiachoff to be equivalents of ooecia. But while according to 

 the description of this author we should think that the cavity of the zooecium 

 itself acts as ooecial cavity, Ostroumoff informs us of the fact, that the em- 

 bryos and larvae are situated in the space between the spines and the frontal 

 membrane. He speaks on this as follows': »The lattice-like zooecium (cellule 

 treillissee Nordm.) serves as ovicell for the zooecium on its proximal side. The 

 cavity of the ovicell is formed on one side by the surface of the mantle (i. e.: fron- 

 tal membrane), on the other by the concurrent spines. The egg, which is ex- 

 truded from the lower zocBcium by the tentacles, comes into this cavity, and 

 this may be easily seen by a transverse section through a lattice-like zooecium 

 containing embryos. Some embryos are usually found in this cavity. < On my 

 enquiry Ostroumoff has however informed me, that he has not observed such 

 a transference of the egg. Besides the ordinary zooecia with 2 — 3 free spines a 

 smaller number may be found, in which the frontal area is surrounded or par- 

 tially covered by 1 — 9 pairs of spines of varying length, which however meet 

 neither the spines springing from the same nor those from the opposite side. 



A number of colonies of this species from Sebastopol were kindly sent to me 

 by Dr. Ostroumoff. 



E. (Heterooecium) amplectens Hincks. 

 Membranipora amplectens Hincks, Annals Nat. Hist., ser. 5, Vol. VIII, 1881, 



pag. 129, PI. Ill, fig. 7. 

 Heterooecium amplectens Hincks, Annals Nat. Hist., ser. 6, Vol. IX, 1892, 



pag. 195. 

 (PI. IX, figs. 1 a-1 c). 

 The ordinary zooecia are pear-shaped oval and provided with a membranous 

 frontal area occupying half the breadth of the zooecium and between half and 

 one third of its length. It is surrounded by seven spines, of which six are short 

 and a proximal one long and strong. From the inner surface of the frontal area 

 more than 30 small dentiform processes issue, of which the two distal ones are 

 the longest. They are arranged in an oval which is not entirely closed proxi- 

 mally, and the distal half of which is immediately within the margin of the 

 frontal area. 



The ooecium-bearing zooecia are broadly oval and have somewhat proxi- 



' 90, p. 19. 



10* 



