X, D, S 



Light: Notes on Philippine Alcyonaria 



209 



a spherical nonstaining body and a half-moon-shaped, darkly 

 staining body — apparently a nucleus. The fact that these 

 bodies are found in the ectoderm and that these Alcyonaria 

 came from a depth of 90 meters makes it improbable that we 

 have here a form of unicellular algae related to those so common 

 in the endoderm of all shallow-water Philippine Alcyonaria. 

 The clear spherical area, however, is strikingly like that sur- 

 rounding the chromatophore in Zooxanthellse, but there is no cen- 

 tral staining area as in these algae. A test for starch would very 

 likely show whether these are algag or not, but unfortunately I 

 have no material to spare for such a test. They may be dif- 

 ferentiated ectoderm cells containing nematocysts of some- 

 peculiar type, the dark-staining body being the nucleus of the 

 ectoderm cell. The nuclei of the typical ectoderm cells are quite 

 distinct (fig. 7), however, and 

 the clear spherule shows none 

 of the structure characteristic 

 of nematocysts. Again they 

 may be some protozoan para- 

 site or symbiote, the clear 

 area being a vacuole. Here 

 and there in the ectoderm of 

 the tentacles are enlarged 

 cells completely filled with 

 small, deeply staining, 

 rounded bodies which may be 

 another stage in the life cycle 

 of such a parasite. Because 

 of lack of material the de- 

 termination of the exact nature of these very curious and 

 interesting little bodies must be left to some future investigator. 



As would be expected in so contractile a form as C. minuta, 

 the musculature is heavy. The ectoderm of the tentacles is 

 penetrated by numerous "muscle banners," which are very con- 

 spicuous in sections of the contracted polyp. The thick ectoderm 

 of the oral surface also overlies a layer of muscle fibers. 



The mesogloea, which is everywhere a homogeneous mass show- 

 ing no penetrating rods of cells as in Xenia and other genera, 

 nor scattered amoeboid cells as in Capnella, Lemnalia, Litho- 

 phytum, etc., is outlined by an outer and inner deeply staining 

 line. In the body wall the mesogloeal layer averages 0.004 milli- 

 meter in thickness, which is about the average thickness of the 

 ectoderm and of the endoderm of the same region. On the oral 

 surface and in the tentacles it is much thickened and sends out 



Fig. 7. An oblique section through the ec- 

 toderm of a tentacle of Cornularia minuta, 

 showing the ectoderm nuclei and the pe- 

 culiar bodies found in the ectoderm cells. 

 X 13.40. 



