500 MR. A. W, WATERS ON 



is formed (fig. 20, z 1-z 3), then the tvibe or opening between the 

 two chambers (fig. 20, z 4) which is at a much lower level than 

 the operculum, next the lip is formed, which at last reaches up to 

 the operculum. The muscles are formed after the opercvilum, 

 and the polj^pide not until after the tube and lip. 



It has not been mentioned that the part between the main 

 sclerite of the operculum is covered by a membrane, thus enclosing 

 a space (fig. 1 7), and the tentacular sheath is fastened * between 

 the two muscular attachments of the operculum, having a tissue 

 across from one muscular attachment to the other (fig. 19, 

 from r-r). As mentioned, the large distal muscle is attached to 

 the operculum, but the large muscle just proximal to it in the 

 A zooecia is fastened by a tendon to the frontal membrane (fig. I'd d) 

 close up to the operculum, wliere there is a slight thickening or 

 sclerite. Harmer t speaks of this muscle as perhaps inserted into 

 the frontal membrane immediately adjacent to the basal sclerite. 



Further back (proximally) there is on each side a diagonal 

 sclerite (fig. 14, sc), to which the tendons of a smaller muscle are 

 attached, which draws down the frontal membrane %. These are 

 called depressor muscles by Harmer §|i. 



In the B zooecia the retractor muscles are much larger than in 

 A, and are in two groups instead of one, but in the present species 

 I am unable to find any very material difi'erence between A and 

 B zooecia. 



The embryos develop at the base of the distal chamber, but 

 this chamber cannot be spoken of as an ovicell, for the polypides 

 are, even when retracted, partly in this chamber. It seems that 

 the embryo may exceptionally be in the proximal part of the 

 zooecium surrounded by a membrane, really an internal ovicell. 

 This requires investigation. 



The first polypide buds in the growing terminations are in the 

 proximal end of the young zooecia as usual, and are nearly always 

 in one of the corners, consequently the polypide grows diagonally 

 across the zooecium, causing a slight amount of asymmetry in the 

 zooecium. The buds of the Bryozoa visually grow from near to a 

 rosette-plate, the position of bud and polypide being thusafiected 

 by the position and number of these plates. In /6'. magnilahris, 

 and probably generally in the genus, there are two large distal 

 rosette-plates. In decalcified preparations a curious large fleshy 



* We must keep in mind that in the Cheilostomata the tentacular sheath is 

 fastened to the operculum and to the zocecial wall. 



f " Morph. of the Cheilostomata," Quart. Journ. Micr. Sc. n. s., vol. xlvi. p. 318 

 (1902). 



X This was not readilj' made out at first, but some thick sections stained in 

 Chlorazol blue enabled me to see it all clearlj-. This is a stain that will be found 

 useful for staining muscles and some other tissue, but it is not a good nuclear stain. 

 Material can be stained and decalcified at the same time, as acid does not affect the 

 colour and it maybe used for intra vitam staining. This stain was given to me b)'' 

 mv friend Mr. Waddington, who has been unable to find out particulars as to its 

 constitution. 



§ Loc. cit. p. 320. 



|] It is interesting to find that the large " pores " in the cryptocjst of Cupidaria 

 oweni Busk are only for the passage of depressor muscles. 



