ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 455 



gullet shows traces of ciliation, and hints of a siphonoglyph both vent- 

 rally and dorsally. In the wall of the polyps there is an indication of 

 nervous elements. The septa show a strong musculature. The dorsal 

 mesenteric filaments resemble the ectoderm ; the ventral (endodermic) 

 mesenteric filaments show ciliated, stinging, and glandular cells. The 

 gonads are either ovaries or testes. 



There are two different kinds of siphonozooids — namely (ajpinnular 

 zooids and rhachidozooids, which are better termed protozooids (arising 

 directly from buds), and (b) metazooids (arising from retrogressive 

 polyps at the apex of the colony). 



The musculature is strongly developed, and may occur in places not 

 usually muscular in Alcyonarians, e.g. the spongy tissue of the rhachis, 

 the epithelium of the main canals, the endoderm of the tentacles, the 

 gullet, and the fine nutritive canals. There is a colonial as well as 

 individual musculature. 



A nervous layer was found especially in the ectoderm of the tentacles, 

 the oral disk, the ectoderm of the gullet, the dorsal mesenteric filaments, 

 the ectoderm of the polyp-wall, and the ectoderm of the rhachis. 

 Endodermic nervous elements were found in the endodermic epithelium 

 of the gullet, the endoderru of the septa, the ventral mesenteric filaments, 

 the endoderm of the cavity of the polyps, of the cavities of the rhachis, 

 and of the main caua s. There is a colonial as well as an individual 

 nervous system. 



The mesoglceal matrix consists mostly of fibrillar elements. It 

 represents a sort of basal membrane or connective tissue " propria," 

 secreted by ectodermic and endodermic epithelium. It includes isolated 

 or grouped mesenchymatous cells mostly derived from the endoderm. 



Niedermeyer gives a full account of the spicules, which are mostly 

 elliptical biconcave rodlets. A few forked forms occur, and twins or 

 triplets. It appears that the compound forms may arise by splitting 

 or by coalescence. The spicules show a centre with radiations, a medul- 

 lary mass, a cortical region, and concentric lines. A spicule arises as an 

 intracellular differentiation within an ectodermic scleroblast. 



The axis shows three zones — an indistinct central strand of longi- 

 tudinal horny fibres closely compacted ; a median zone mostly of 

 longitudinal fibres with some spicules, and an external zone with con- 

 nective tissue in process of transformation, showing concentric lines and 

 remains of cells and spicules. There is a mesoglceal axis-sheath and an 

 apparently endodermic axis-epithelium. The facts point to the conclu- 

 sion that the Pennatulid axis is mesoglceal, not endodermic. The 

 intraseptal spaces are mesoglceal and not connected with the gastral 

 cavity of the primary polyp The histological facts support the view of 

 Kiikenthal and Broch that Veretillum is one of the most primitive 

 Pennatulids. 



Minute Structure of Ovarian Ovum of Aurelia aurita.* — R. Tsu- 

 kaguchi describes (1) the small densely-packed oogonia, with usually 

 sparse spherical plastosomes in the vicinity of the nucleus ; (2) the 

 young oocytes, with larger nucleus, some yolk-spherules, fine irregularly 



* Arch. Mikr. Anat., lxxxv. (1914) 2te Abt., pp. 114-23 (1 pi.). 



