LOXOSOMA. SbO 



period. The structure of the latter may be traced in such an 

 ovum as the one marked 9 in Figure 6. It takes on a very broad 

 form, the circumference has become transparent, whilst in the 

 centre an opaque mass is visible, which is in connection with the 

 periphery at a single point. At a later stage a funnel-shaped 

 depression, clothed with very delicate cilia, makes its appearance 

 at this point and constitutes the mouth. 



The Author has fully satisfied himself that the central, opaque, 

 flask-shaped mass (PI. XXII, fig. 6) presenting a mammillated ap- 

 pearance, owing to the large seed-like cells of which it is com- 

 posed, has at first only a single point of communication with the 

 periphery. Its posterior extremity, which is broad and rounded, 

 is always bordered by a clearly defined outline at some distance 

 from the periphery. This opaque mass is, as it were, the first 

 rough draught of the digestive canal ; it follows that in the ffasfrula 

 the digestive canal is a cul-de-sac and destitute of an anal orifice. 



The Author next describes in detail the perfect larva (PI. XXII, 

 fig. 7), remarking upon the difficulty of giving an accurate sketch 

 of a creature which is so rapid and erratic in its movements, and 

 changes its shape so continually .^ 



In its usual condition, when expanded, it resembles a very 

 wide bell, the thickened border of which is formed by a wreath of 

 loug cilia, with a clapper-like body projecting in the centre. 

 Near the enlarged and rounded summit of the bell are two red 

 eye-specks situated near the edge of two circular depressions, 

 surrounded by an elevated border from which a few setiform 

 cilia rise. The eminently retractile clapper bears a central 

 mouth, surrounded by four eminences, and at the opposite 

 extremity of the bell is a button-shaped caudal projection, also 

 retractile and furnished with a few stiff cilia. 



Passing to the details of the structure, the clapper, which may 

 be called the buccal mammilla (0), can be withdrawn entirely so 

 as to leave a kind of funnel, but usually has the form of a trun- 

 cated cone, the extremity of which is furnished with very long 

 cilia, while the margin of the buccal cavity and the cavity itself 

 are clothed with extremely delicate and short cilia. The margin 

 is divided into four rounded lips. The mammilla, like the rest 

 of the body, is composed of two dermic layers, a transparent 



' I have experienced the same difficulty when attempting to master the 

 external characters of the kindred Pedicellina embryo. Its restless activity, 

 its rapid and irregular motion, and the frequent changes of form in its 

 eminently contractile body, made it no easy matter to gain any clear i<iea of 

 its actual appearance. It was necessary to make the most of the occasions 

 on which it anchored itself for a few seconds by means of the ciliated base 

 of the body. It is hardly wonderful, under the circumstances of the case, 

 that there should be differences between the reports of competent observers. 

 — Transl. 



