PORII-ERA. II. 



like, and accordingly they are isochelae. In ancorse spatuliferae the ends, as far as known, are always 

 like, they are isancorae, while ancorse unguiferae may be isancorae or anisancorae. 



According to the preceding the chelate microsclera may be divided into the following forms: 



Cheke 



palmatse arcuatae 



aniso- iso- 



Ancorse 



spatuliferae unguiferae 



most frequently 3—9 teeth 

 3 teeth 





1S0- 



1SO- 



amso- 



AU forms of microscleres belonging here may always be referred to one of the types chelae or 

 ancorae. This does not seem to be generally acknowledged. Thus the small chelae characteristic of 

 the genus Asbesiopluma have given rise to different interpretations, but in reality they are constructed 

 on the same principle as the other chelae. Even so deviating a form as the chela in Mycale thauma- 

 tochelcE described below is of the same fundamental structure, and this holds good also with regard 

 to the peculiar wry chela in M. Utubans; nay, even the bipocilla in the genera lophoti and Pocillon 

 may be referred to the same form. Top sent (1 c. fasc. XXV, 209) proposes the term placocheles> for 

 the peculiar palmate isochelae in Gziitarra and Esperiopsis villosa; I cannot, however, see any reason 

 for a special name for these forms, as they are typical isochelae palmatae. A typical chela thus con- 

 sists of the following parts, which I designate by the following terms, generally in use: a shaft or an 

 axis having in either end a bending, the tooth, and at either end two lateral extensions, the alae; 

 between the shaft and the tooth, at a right angle to these, is found a plate-shaped part, falx, and the 

 thickened part of this structure shining through the fore side of the tooth, is called tuberculum. In 

 ancorae quite the same parts are found, the only difference being that in these several teeth are found 

 each with falx and tuberculum. 



With regard to the development of these forms many misconceptions have been advanced. As 

 early as in 1857 Bowerbank (Phil. Trans. Roy. Soc. London CXLVIII, 304) and later in the first 

 volume of Monograph 1864, 47, PI. VI, fig. 144— 147, has given a description with figures of these 

 forms, which, to be sure, is not correct, but nevertheless rather good and free of the misconceptions 

 arising later, as he has clearly understood that the first beginning was of the same length as the 

 fully developed spicule. Also O. Schmidt in 1862 (Die Spong. des adriat. Meer., 8), although he does 

 not understand the growth of these spicules, has seen that small and large chelae occurring in the 

 same sponge are not stages of growth of the same form. Later the misconceptions appear. Carter, 

 in 1874 (Ann. Mag. Nat. Hist. 4, XIV, 100), advances the view that the anisochelae begin as isochelae; 

 he has been led to this view by the fact that he upon the whole regards small isochelae, in a species 

 also provided with large chelae, as younger stages of these, and so he is led to suppose a growth 

 with the most peculiar alterations of form. That Carter has not later been quite sure of the correct- 

 ness of his theory may be seen from the fact that in 1882 (Ann. Mag. Nat. Hist. 5, IX, 298) where he 



