334 Transactions. — Zoology. 



Plate XXX. 

 Cystodytes attcklandicus and C. perspicuus. 



Fig. 1. Portion of test showing spicules, calcareous trees (c.t.), fibres (c./.), 



and calcareous bodies (c.b.). Enlarged 7 diameters. 

 Fig. 2. Zooid of C. aucMandicus. Zeiss a*, enlarged. 

 Fig. 3. Detail of test in C. perspicxLUS, Z. C, camera. 

 Fig. 4. Calcarsous spicule (tree) of C. aucklandicus. Z. A, camera. 

 Fig. 5. Calcareous crystals of C. ycrspicuiis. 7i. A, camera. 

 Fig. 6. Detail of form seen in fig. 4 under high magnifying power (Z. E). 



Drawn without reference to scale. 

 Fig. 7. Detail showing calcareous bodies forming radiating branches. 



Seen in unstained sections. 

 Fig. 8. Crystalline branching calcareous bodies from the region of the 



capsule. Z. A, much enlarged. Glycerine. 

 Fig. 9. Spicules from C. perspicuus. Z. A, camera. 

 Fig. 10. Surface-vessel in the test from Cystodytes attcklandicus. Z. C, 



camera. 

 Fig. 11. Branchial siphon with part of branchial basket of C. perspiciLUs. 



The upper part of the basket has been removed in sectioning, 



leaving the lower surface visible from inside. Z. C, camera. 



Aet. XXVI. — On the Structure of Boltenia pachydermatina. 



By James Watt, M.A. 



From the Biological Laboratory of the University of Otago. 



[Read before the Otago Institute, 11th Aiigust, 1891.] 



Plates XXXI.-XXXIV. 



This species of Boltenia is found attached to rocks, piles, 

 shells, &c., or lying loose on the sea-bottom. In the latter 

 case, as a general rule, the specimens have become detached by 

 the breaking of the stalk some distance from the base. Very 

 often they are seen in bunches in masses of seaweed, in which 

 cases, however, they are not directly attached to the seaweed 

 itself, but have become united to it by the entangling among 

 the seaweed of the shell or other base of attachment to which 

 they have united themselves. The members of this species 

 are often seen growing in bunches, when either a number have 

 attached themselves to a shell or some such small base of 

 attachment, the stalks becoming fused at their bases, or a 

 number of younger specimens have fixed themselves to the 

 stalk of a larger. 



Anatomy. 



A. External Characters. 



A. — The body is somewhat ovate in shape, compressed 

 laterally, slightly concave on the dorsal border, convex on the 

 ventral. The posterior end is bluntly pointed, the anterior is 

 narrow, becoming gradually continuous with the stalk. The 



