BllYGZOA FROM ZAXZI15AK. 499 



According to Hanner the A zocecia are in most species of 

 Steganoporella more abundant than the B, and he says there are 

 no B in S. simplex H., and goes on to say that they are rare 

 in S. sulcata H., S. lateralis H., and S. •niagnilabris B. In 

 S. truncata KT. the ratio of A to B is 4-5 to 1 ; on the other hand, 

 in S. alveolata H., there are few A zooecia, and *S'. connexa H. has 

 only B zocecia. 



As Harmer* has shown, there is considerable difference in the 

 teeth of A opercula of magnilabris from various localities, and we 

 have opercula of this Wasin specimen without any, also the B 

 opercula may be with or without lateral teeth. The A opercula of 

 a ' Challenger' specimen (208-90-4.16.13) has the teeth so minute 

 that they would be overlooked with a low power, but are seen 

 with a quarter-inch objective. 



The operculum of Steganopoyella can scarcely be compared with 

 the opercula of other Bryozoa, as it closes the whole of the distal 

 chamber', and in a zoarium there is an amount of variation in size 

 of the opercula which is unknown in other genera of Bryozoa. 

 In a British Museum specimen of &'. truncata Harm, from Port 

 Dalrymple, there are a few cases where the operculum is thrown 

 back, and then the whole of the opercular opening (that is over 

 the distal chamber) is covered by a membrane with a, large round 

 opening, thus furnishing a most interesting form of closui-e. 



The wall, dividing the two chambers, passes vertically from the 

 opercular wall to the basal wall, and in the middle there is a 

 round opening, sometimes with a slight tubular projection through 

 which the polypide passes. The polypide rests partly in the two 

 chambers, that is the tentacles are not entirely withdrawn into 

 the proximal chamber. The embryos develop at the base of the 

 distal chamber, but this chamber can by no means be spoken of 

 as an ovicell. 



The Wasin specimens show some blind zooecia either entirely 

 closed or with a central opening, and the same occurs in a speci- 

 men of S. tubulosa H., where two zooecia are about the normal 

 size, one with a large round opening, the other with an oval one, 

 and in these the whole of the frontal wall is granular. On the 

 other hand, a British Museum specimen of S. sulcata H. has two 

 zooecia entirely closed by the perforated cryptocyst. 



The S. magnilabris from Wasin has floating in the pr-oximal 

 chamber many small oval bodies, surrounded by a membrane 

 containing diatoms and other detritus. These are the excre- 

 ment pellets, and they are evidently frequently ejected within 

 the zooecium. 



Stud 3^ of the growing ends is instructive. At first there is 

 an absolutely empty oblong zooecium covered with a plain mem- 

 brane, and in this either A or B opercula may be formed, but at 

 first the operculum has no basal sclerite (fig. 20), as this is 

 formed subsequently. Next the proximal part of the cryptocyst 



* Loc. cit. p. 2iL 



Proc. Zool. Soc.—lOlS, No. XXXIV. ;J4 



