THE CRYSTALLINE STYLE OF LAMELLIBRANCHIA. 595 



that the crystalline style cannot be legavded as a rudimentary 

 structure, is that it is an active amylolytic ferment, as we 

 shall see presently. Only if we could regard the ptyalin or 

 the pepsin of other animals as a rudimentary structure, could 

 we take the crystalline style as a rudimentary structure. 



Let us now describe and state fully the physical, chemical, 

 and physiological characteristics of the crystalline style, 

 that is to say, see what it really is and what it really does. 

 After we have done that we shall dispose of the third and 

 the fourth hypotheses. 



A fully-formed crystalline style that has been shed some 

 twelve hours is a flexible, solid transparent body that is 

 thicker at one end than at the other. Broadly speaking its 

 form is like that of a slender cone (see figs. 1, 2, 4, 5, 6). 

 Under the microscope it is seen to be longitudinally striated 

 (see figs. 4, 6). The striation is due to the fact that the style 

 is composed of concentric or rather co-axial (placed rouud a 

 common axis) layers of a colloid substance of greater and 

 lesser density. A cross section of a fully formed style looks 

 under the microscope like the cross section of an onion (see 

 fig. 3). We must state here that very often one notices in 

 the style of Anodon a central much softer core, which is much 

 less perfectly striated, and which lias embedded in it particles 

 of food material (see fig. 5). In a freshly formed style in 

 Anodon, that has been shed a few minutes ago, this central 

 core forms a very marked feature. Under the microscope 

 it is seen to occupy three fourths or more of the space 

 occupied by the whole style, that is to say, to possess a 

 diameter tliat is three fourths or more as long as the diameter 

 of the whole style at the corresponding part; to be a viscous 

 liquid of a finely bubbly appearance; and to be surrounded 

 by a comparatively thin nearly homogeneous sheath-like 

 layer (fig. 5). In fact, such a freshly formed style may 

 briefly be said to be formed of a viscous liquid that has got 

 formed round it, apparently through condensation of its own 

 substance, a thin sheath-like layer. This observation is very 

 important, as showing that a fully-formed style is not pro- 



