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PLATE XLI. 
PAGE 
Figs. 1-4. Disyringa dissimilis, . . . . .161 
1. The sponge; nafc. size. On the right of the upper end of fig. IcZ a section is shown of the 
cloacal tube ; in a corresponding position at the lower end a transverse section of the 
poriferous incurrent tube; fig. 15 represents the termination of the cloacal tube; the 
sponge of fig. Ic possesses the longest incurrent tube observed, and this is not complete. 
2. The sponge, restored from the fragments shown in the preceding figure ; nat. size. 
3. A diagrammatic median longitudinal section through the sponge ; nat. size, a, A transverse 
section through the cloacal tube ; 5, a transverse section through the incurrent tube ; c, a 
transverse section through the sponge in the region just where the incurrent tube divides 
after entering the sponge. 
4. Transverse section through the body of the sponge, showing the symmetrical arrangement 
of the excurrent and incurrent canals which alternate with each other. I, incurrent, E, 
excurrent canals ; x 4. 
5. A facial view of the waU of the excurrent tube of Trihrachiwn sehmidtii, seen from without ; 
X 73. (The figure would answer as well for the excurrent tube of Disyringa dissimilis.) 
6. The sponge ; nat. size. 
Figs. 6-21. Tetilla pedifera, . 
7. Section at right angles to the surface, showing 
clusters will be observed in places ; x 73. 
the folding of the spongophare ; sperm- 
12. Spicules — 
Fig 8. Anisocladal p'rotriaene ; x 180. The 
rhabdome of this should have been 
represented as broken at the centri- 
petal end. 
„ 9. Promonsene j x 180. 
Fig. 10. Cladal end of anisocladal prodisene ; 
x 180. 
,, 11. Cladal end of anisocladal protriaene ; 
x 180. 
,, 12. Cladal end of an anamonsene ; x 180. 
13. Spermatoblast; x 292. 
14. The earliest stage of segmentation observed ; x 292. 
15. A developing sperm-cluster; x 292. Fig. 15a, a few of the segmentation cells of the 
preceding, more highly magnified ; x 576. 
16. Sperm-cluster, almost mature; x 292. Fig. 16a, some of the developing spermatozoa, more 
highly magnified ; x 576. 
17. A sperm-cluster in a stage somewhat later than that of fig. 15 ; x 292. Fig. 17a, some of the 
segmentation cells, more highly magnified ; x 576. 
18. Sperm-cluster in a stage more advanced than the preceding ; x 292. 
19. An abnormal appearance presented by a sperm-cluster; x 292. 
20. A mature spermatozoon ; x 576. 
21. A problematical body, apparently the segmentation of an ovum; x 292. 
6 
