530 REPORT ON THE XENIIDAE COLLECTED BY DR WILLEY. 



from the inner side (see the tentacle on the left) two rows of pinnules are visible on each 

 side of the middle line, a third row will be formed later. This is typical of the buds of 

 the Xeniidae. x 15. 



Fig. 11. X. umbellata. A bud from the middle portion of the summit of a stem. The 

 body of the young polyp has grown much larger in proportion to the tentacles than is 

 usual. The total length of the polyp is 6 mm., its slender linger-like tentacles are 1-.5 mm. 

 long and bear only one or two pinnules on each side. The tentacles of this and of the 

 specimen shown in Fig. 10 are equal in length. See also p. 514. x 15. 



Fig. 12. A', umhellata. A bud 5 mm. long from the middle portion of the summit of 

 a stem. This is similar to, but probably younger than the one shown in Fig. 11. The 

 body is very stout, the tentacles are somewhat unequal and measure I'O mm. to 1-3 mm. in 

 length. Some of them (on the left) are trilobed at tlieir free ends, i.e. there is an indication 

 of the formation of the first two pinnules. See also p. 514. x 15. 



Fig. 13. X. umbellata. Thin section (5/x) of an ovum probably almost mature. The 

 peripheral zone of protoi)lasm is finely granular and devoid of yolk spherules, the central 

 mass of protoplasm contains many cavities, which in life probably contained the }'olk spherules. 

 For further description see p. 515. x 200. 



Fig. 14. Xenia viridis. Portion of a thin section of a mesentery which bears male 

 and female products. On the right the mesentery is cut almost longitudinally, showing in 

 the mesogloea (Mg.) the cells {Gen. C.) with well-marked nuclei and reticulate protoplasm 

 which give rise to genital products. In the centre of the figure are several very young 

 sperm sacs, each of which contains a few cells produced by division of one of the primitive 

 genital cells. Below and on the right is a large sperm sac containing many hundreds of 

 sexual cells which after a very few more divisions would give rise to spermatozoa. To the 

 left of the sac is one of its genital cells more highly magnified (x 2000) to show the large 

 nucleus (X.). On the left of the figure are four young ova (Of.) each in its follicle of 

 endoderm (End.). Each has a well-marked germinal vesicle ((?. V.) and germinal spot. The 

 small cavities in the somewhat granular pi'otoplasm probably contain yolk spherules in 

 life. X 320. 



