590 ALEXANDER MEEK 



them. But they are enclosed in a mucous-hke secretion 

 probably derived from the ectodermal gland-cells of the 

 atrial cavity. The secretion, however, is present in the 

 neighbourhood of the pore and plays its part in directing 

 the sperms laterally. The mass is tucked in within the spa'ce 

 formed by the margin of the genital wing and spreads out- 

 wards as a thin sheet outside the marginal flap. The anterior 

 gonads appear to discharge their contents before the posterior 

 and the loft before the right. In the sections the sperms 

 may be easily seen issuing from the gonopores and joining 

 the mass below, a mass containing countless numbers, each 

 having the usually flagellate shape with a rounded head. 



Besides the sperms the gonadial sacs are occupied by bodies 

 which are highly refringent and eosinophile, and in the latter 

 respect in striking contrast to the sperms. Like the sperms 

 they arise in marginal cells and become detached. They 

 vary greatly in size and appear to have a protoplasmic 

 envelope, and the bodies, though usually apparently homo- 

 geneous, have sometimes an appearance as if they were made 

 up of a mass of smaller bodies. They are not as far as can be 

 seen nucleated. In the undischarged or partially discharged 

 folds of the gonad they surround the mass of sperms which 

 occupies the centre, but small groups of sperms are found 

 amongst them peripherally. In the discharged parts of 

 the gonads thej^ press into the interior, but whether this is 

 due to collapse of the tube or to actual multiphcation could 

 not be said. A few escape with the sperms and are seen in 

 the atrial mass and there appear to lose gradually their 

 eosinophile character. In the gonads also here and there 

 are large cells of the margin which project into the cavity 

 each provided with a large nucleus containing a large 

 nucleolus. The refringent bodies have been observed in other 

 specimens of Enteropneusta, and so far as can be said at 

 present they may be regarded as nurse-bodies. 



It is possible that the peculiar condition of the atrial 

 cavity is due to the fact of the discharge of the sperms. 

 In the male the apposition of the genital wings may be 



