234 M. Curl Cliun on the Formation of 



and there is no reason to suppose that it degenerates and is 

 subsequently replaced (Semon) by means of the cells of the 

 ciliated band or of the peripheral connective tissue. 



A richly vacuolate plasma at once distinguishes the skeleto- 

 genous cellsj the average size of which is '01 millim. They 

 rapidly grow to twice and thrice this bulk, while simulta- 

 neously the number of the cell-nuclei increases. In the same 

 Anricularia we meet with all intermediate stages between 

 uni- and multinucleate cells, which at first still retain a 

 rounded contour, but subsequently flatten out on one side and 

 become cup-shaped. The nuclei measure from "003 to '004 

 millim in length, and originally (so long as only from two to 

 four are present) occupy a peripheral position ; they after- 

 wards increase to from six to eight in the case of the Medi- 

 terranean Auricularice, and to from twelve to eighteen in that 

 of those from the Canary Islands, and form a central nuclear 

 cluster. 



When the cells have attained a size of '03 millim. there 

 appears within the old cell-membrane a new one, which has 

 an undulating outline towards the circular margin and speedily 

 assumes a star-shaped form. The tubular rays of the star 

 which grow out are equal in calibre and meet the external 

 membrane, arching forward somewhat at the points of contact. 

 The longitudinal extension of the radially arranged out- 

 growths keeps pace with the increase in the size of the cell, 

 and finally, when the cell attains a size of from '06 to '07 

 millim., the rays become united by a peripheral membranous 

 ring. It is now impossible to mistake the mould of the 

 subsequent calcareous wheel, prepared as it is by the complex 

 folds of an internal membrane : the central portion with the 

 cluster of nuclei corresponds to the nave, the tubes running 

 out like the rays of a star represent the spokes, and the peri- 

 pheral ring takes the place of the circumference (the felly) of 

 the future calcareous wheel. Moreover the calx is actually 

 secreted into this organic matrix formed by the skeletogenous 

 cell, as into a mould, and in such a way that (as the older 

 accounts already teach us) calcification takes place first in 

 the nave, then in the spokes, and finally in the felly of the 

 wheel. It is likewise in accordance with the theories which 

 have recently been formulated as to the share of the nuclei in 

 the vital processes of the cell that, corresponding with this 

 centrifugal progress of the calcification, the majority of the 

 cell-nuclei also separate from one another in a centrifugal 

 direction, and in the case of the Auricularice from the Canary 

 Islands come to lie in the acute angles between the spokes. 



