536 ME. G. C. BOUENE ON THE GENUS LEMNALIA AND 



Finally I have a few words to say on the formation of huds in LemuaUa. A bud, 

 from which a new zooid grows, is always formed on a solenium which reaches out 

 towards the surface. An early stage is shown in fig. 22. The solenium, sol., expands 

 close to the surface to form a wide cavity, the body-cavity of the future zooid. The 

 endoderm-cells lining the outer wall of this cavity become longer and more columnar 

 than in other parts ; their nuclei arc more numerous and stain more readily, and 

 numerous zooxanthellse are accumulated in them. The outer wall of the cavity is only 

 separated from the ectoderm by a very thin sheet of mesogloea, and outside this the 

 ectoderm proliferates rapidly, forming a solid plug, which carries tlie mesogloea and 

 endoderm before it towards the interior of the cavity. This plug is the beginning of the 

 stomodseum (tig. 23, st.). In the next stage the mesogloeal lamina at the bottom of 

 the plug is broken through and the ectoderm becomes continuous with the endoderm ; 

 the centre of the plug becomes hollowed out, and the cells arrange themselves as an 

 epithelial lining of the tube thus formed. The mesenteries make their appearance at 

 an earlier stage as folds of the elongate endoderm-cells at the lower end and sides of the 

 still solid plug (fig. 23, mes.). Shortly after the stomoda.Him has become a hollow tube, 

 the cells at its lower end are differentiated to form the elongate columnar ciliated 

 epithelium already described (fig. 24, st."). The oral disc and tentacles are developed 

 subsequently, the latter as simple digitiform outgrowths of all three layers in the 

 neighbourhood of the mouth. 



I have elsewhere referred to the minute structure of the spicules of LemnaUa * . The 

 elongate fusiform spicules are excellent objects for study, because of their small size and 

 transparency. Fig. 17 shows that each has an axial core, from wliich offsets radiate 

 outward, nearly at right angles to the core, and every such offset forms the centre of 

 one of the sj)inous projections. In some of my sections tlie organic matrix of the 

 spicules was well preserved, and stained deeply with htematoxylin. This matrix consists 

 of an external sheath and a central branching axis of organic fibrils which correspond 

 exactly to the axial core and its offsets as shown in figs. 17, 8«, and 11 h. The spicules 

 have, in fact, exactly the same structvu'e as those of Sjwngodcs, described in detail in my 

 paper referred to above. 



The more important points dealt with in this pajierare: — 1. The description of the 

 branching-systems of the Alcyonacea in general and of LemnaUa in particular. 2. The 

 restoration and amended description of Gray's genus LemnaUa, with an account of some 

 new species. 3. The occurrence of a narrowed, uniformly ciliated tube in the lower 

 part of the stomodseum of LemnaUa. 4. The oi'igin of the scleroblasts and the growth 

 of the mesoglcea in this genus. 5. The manner in which new zooids are formed from 

 solenial outgrowths, ti. A new set of descriptive terms applicable in particular to the 

 Order Alcyonacea. 



Oxford, January 14. IbUD. 



* " The Stnuture and roiOiiitiou of tlic Cnlcaifoiis Skeletc ii in the Aiitliozoa," Qiuirt. .loiini. Slici-. Scicrico, vol. >;Ii.^ 

 (1899), p. 499 



