10 MADEEPOKAEIA. 



The only paper which I have found dealing with the anatomy of a Turbinarian is by 

 Dr. f!. Herbert Fowler* 



A fragment, belonging "apparently to the type T. mesentcrina," showed that (1) the 

 poly|3s are of the normal Actinian type, are bilateral, the axial and abaxial directive mesen- 

 teries being placed approximately in a plane running at right angles to the growing edge 

 of the corallum. These are distinguished by the arrangement of retractor muscles on their 

 ectocoelic faces. The polyps, however, are not rigidly bisymmetrical, inasmuch as the pairs 

 of mesenteries lying right and left of the dividing plane are not equal in number. 



(2) The septa are entoccelic only, although a misleading appearance of ectocoelic septa is 

 produced by the fact that some pairs of mesenteries die out after a very short course, while 

 their septa are still recognisable at a much greater depth in the polyp-cavity. 



(3) The tentacles are probably entoccelic only. In the contracted condition, they are 

 covered by a ring-fold formed of the indrawn margins of the disc. 



(4) The whole colony, both inside and outside, is clothed with an external body-wall 

 of ectoderm ; this wall rests upon the ecliinulations of the coenenchyma. 



(5) Nematocysts are closely packed together in the tentacles, not, however, arranged 

 in knobs or " batteries." 



(6) Zooxanthellic are present abundantly in the canals exterior to the theca, in the 

 tentacle-cavities, and immediately under the mouth-disc ; elsewhere they are comparatively 

 rare. 



MORPHOLOGICAL. 



Description and Definition of the Genus hctscel iipon the Examination of the Hard Parts. 



Eise and Growth of the Corallum. — The earliest known stage in the development of 

 Turhinaria is typically a minute cup. This form is apparently the natural result of the 

 method of budding of the original parent polyp, and of the secondary budding of these buds. 



A cross-section through the stem of a young cup shows a large central polyp, which is 

 that of the parent polyp of the colony. This is surrounded by a great thickness of light 

 spongy ccenenchyma forming the main support of the cup. This layer may be described as 

 built up of long, radiating, perforated costse (which continue very irregularly the radiation of 

 tlie septa), bound together by tangential trabeculaj. 



From this original polyp, a single ring of new polyps bud laterally, either at or near the 

 same level. These buds grow out at an angle from the original parent polyp, which then 

 appears itself to die down ; in no case does it continue to grow like the axial polyp in 

 Madrepora, budding forth successive rings of daughter polyps. As stated, the axial parent 

 polyp in Turhinaria appears to die down, and the colony is carried on exclusively by the ring 

 of daughter (and sometimes at least smaller) polyps. These, again, develop buds on the side 



* 'Anatomy of the Madreporaria,' pt. iii. Quart. Journ. Micro. Sci., xxviii. p. 1. 



