PLATE VIII. 



Polytrema miniaceum (Linne). No. 608. 



Note. — Figures 7, 24, and 29 were drawn from Corsican .specimens. 



Fig. 1. — Earliest observed stage, lying on sponge but ajiparently not attached. 



Figs. 2, 3. — Very early stages of the free form. 



Figs. 4, 5, 6, 7. — Develojjment of the free form into the "" rasjpberry " stage. Fig. 7 marks the ultimate 



possible develoiMuent, and was not observed in the New Zealand material. 

 Fig. 8. — The free "" ras])berry "' form becomes sessile. At this early stage the pavement layer of chambers 



by which it attaches itself is not visible from above. 

 Fig. 9. — A sjjecimen similar to Fig. 8, detached to show the ruptured pavement layer of chambers. 

 Fig. 13. — ^A partial section through a specimen slightly more advanced than Fig. 9, showing the " rasp- 

 berry " in a nest of jjavement chambers which are commencing to form outgrowths. 

 Fig. 10. — A more advanced specimen which has been attached to the rounded stem of a Zoophyte. The 



pavement layer and its outgrowths have entirely envelojsed the " raspberry," 



forming two tubular outgrowths, and are spreading round the stem of the host. 

 Figs. 11, 12, 14. — Stages in the development of the pavement and investing layer of chambers, and 



the formation of tubular ajsertures. 

 Figs. 1.5, 16, 17. — Further stages of develojiment involving the final disappearance of the " raspberry " 



in the investing layers. 

 Figs. 18, 19, 21, 22.— Tradition stages up to the adult. 



Fig. 20. — Section through primordial chambers of the free " raspberry "' stage. 

 Fig. 23. — An adult specimen attacked by an organism which has tunnelled into the hard test. 

 Fig. 24. — A similar specimen (from Corsica) in which the ravages of the boring organism have exposed the 



" raspberry," which, owing to its thicker test, has been left untouched. 

 Fig. 25. — Adult stage, section showing concentric layers of investing chambers in trunk. 

 Fig. 26. — Detail of surface-layer from Fig. 25, showing the reticulate character of each investing layer of 



chambers. The round pits are the first stage in the formation of " pillar pores." 

 Figs. 27, 28. — Partially decalcified basal portions in which the position and structure of the '' rasjjberry " 



are clearly shown. The thick chitiiious linings of the chambers of the rasj^berry have 



resisted the process of decalcification. 

 Fig. 29. — Basal view of a part of the base of a microspheric sjsecimen, showing rotaline initial chambers. 

 Fig. 30. — A jmrtially decalcified specimen viewed from the base and .showing the chitinous lining of 



the pavement layer of chambers which had attached the " raspberry " to its host. 

 Fig. 31. — A fragment of Polytrema with envelopment of large sponge-spicules, perhaps due to symbiosis 



of the two organisms. 



Magnifications— Figs. 1, 2, 3, x 50. 



„ 4 to 14, 24, X 40. 



„ 15 to 19, 26 to 28, x 30. 



,, 20 and 30, x 60. 



„ 21 to 23, 2.5, x 15. 



„ 29, X 90. 



„ 31, X 25. 



