986 



MR. R. KIRKPATRiCK AND DR. 3. MfiTiZELAAR, 



other than a South American representative of Membranipora 

 membrmiacea L. 



The study of the triang-ular objects in C. lacroixii Audouin 

 and in the early stages of C. commensale Kirkpatrick & 

 Metzelaar has, we think, thrown an interesting light on certain 

 structures found in widely sepai-ate families and genera. The 

 precise nature of the " triangular hollows"' * in C. lacroixii is not 

 definitely known, but the view that they are diminutive zocecia, 

 aborted owing to exigencies of space, appears to us a reasonable 

 one. Cramped zooecia are often found among the rows and layers 

 of ordinary zooecia. The openings of the inter-zooecial triangular 

 hollows of 0. lacroixii have granulated margins, precisely com- 

 parable with the edges of ordinary zocecia, and under a high 

 power the whole structure is fairly similar in aspect to an 

 ordinary zooecial box somewhat distorted. 



In C. commensale the triangles have a calcareous roof, and are 

 bounded each by a separate brown line. Where the triangles 

 are fused into one rectangular block, there is only one line round 

 the block. A fundamental and — ^with the exception of Loxo- 

 soma — universal character of the Polyzoa is that of budding 

 so as to form colonies. Limitation of space must lead to a 

 struggle among the buds, with partial or complete suppression of 

 some. 



It would appear that in C. lacroixii each zooecium gives off 

 three distal buds, the lateral ones being almost, but not wholly, 

 suppressed. 



A careful examination of many species of Cheilostomes has 

 convinced us that the paired spaces, knobs, tubercles, and spines 

 so commonly present are all comparable with the " triangular 

 hollows " of G. lacroixii, and that they are modified zocecial 

 buds t taking on strange shapes and functions. In Mer)ihranipora 

 Tuemhranacea L., for instance, triangular spaces will be found at 

 or near the growing edges of the zoarium ; in older cells the 

 " hollows " (really inter-zooecial boxes) grow up into long spines 

 or tubercles, as if, owing to the limited basal area, they took to 

 building skyscrapers. 



In M. teli%ielcha d'Orbigny (fig. 12) the same event has 

 happened. Here the tops of the spines are often membranous, 

 recalling the membranes over the openings of the triangles in 

 C. lacroixii. That this interpretation is not a mere fancy, is 

 shown by the resemblance of the early stages of the spines 

 near the growing edges of colonies to the triangular areas in 

 (7. lacroixii. 



In M. tuhercuXata Eosc, so abundant on Gulf weed, the 



* Hincks, 'British Marine Polyzoa,' p. 130. 



f Cf. the " origellse " of Jullien, " des bourgeons charmis, developpes sur I'endo- 

 cyste,' 'which can reproduce zooecia, avicularia, etc. (Bull. Soc. Zool. France, xi. p. 607, 

 1886). Later, " joncturies," which produce zooecia, are distinguished from " origelles 

 evolutives," which form avicularia, spines, etc. (Jullien & Calvet, Bryozoaires 

 ' Hirondelle,' 1903, p. 18). 



