142 



PEOF. ST. GEOEGE MIYAIIT 01^ 



The complex nucleus is a small vesicle (the '^Bmnenhldschen'* 

 or " vesicula intima " of authors) formed of porous membrane 

 similar to, but still more delicate than, the capsule itself. It may 

 be simply spheroidal, or it may be produced on all sides into a 

 number of rounded processes, as in Thalassicolla, and still more in 

 Myxobrachia (fig. 3). Its contents are mainly clear and homo- 

 geneous ; but Hertwig has shown that minute bodies become de- 

 veloped within it, which he considers to be nucleoli, and which are 

 said to pass outwards through the membrane and to grow into and 

 become the simple nuclei before described. Fari passu with this 

 extrusion of nucleoli and consequent multiplication of nuclei, the 

 vesicula intima shrivels. This complex nucleus has as yet only 

 been found in the genera ThalassicoUa, Thalassolampe, Myxohra- 

 cliia, Physematiim, Aulacantha, AuIospJicera, Heliosphcera^ and 

 doubtfully in Diplosphcera. 



Besides the mxoXQi, fatty bodies (formed of albuminoid substance 

 and adipose matter) are also present in most cases, but are ge- 

 nerally absent in young individuals. These fatty bodies have 

 mostly the form of a relatively larger central body with smaller 

 ones scattered round it ; and when tbe capsule is elongated in 

 shape, it has generally one such body near each end. 



The intracapsular sarcode may appear colourless and transpa- 

 rent, as in HeliospJicera, in many kinds of Acanthometra, and 

 others, or it may seem strongly coloured. The commonest 

 colours are yellow, red, or brown ; but purple, violet, blue, or 

 olive-green are found in a few species. Two colours rarely co- 

 exist in one capsule. In Spongocyclia and Spongastericus the inner 

 part of the capsule is scarlet and the outer part golden yellow. 

 The sarcode is not itself coloured, nor does it contain coloured 

 fluids. The pigment exists in granules or small vesicles. 



In a very few genera {ThalassicoUa, TJialassosphcera, Acanthochia- 

 sina, and at least one AcantJiometra) we find scattered in the sarcode 

 small bodies called " concretions,'' in the form of round or elliptical 

 disks, the sides of which may be flat or more or less strongly con- 

 vex *. In ThalassicoUa these concretions, and also fatty bodies, 

 appear environed by, or connected with, certain peculiar bodies 

 of doubtful nature, to which the name "JEiweissJcugeln " has been 

 given t. The concretions consist of leucin J and tyrosin§, and 



* See Haeckel's ' Eadiolarien,' pi, iii. fig. 3. 

 t Hertwig, ' Histologie,' table iii. fig. 9. 

 t C,H,,(.NH,)0,. § C,H„ N03. 



