20 Mindeskrift for J. Steenstrup. XXV. 



of an insignificant deviation in distance on both sides, not even 10/^, I suppose. The 

 exact proportion can not easily be given in fixed numbers, the torsion of the tail pre- 

 venting its being placed in one plane. 



The two spicules are exceedingly different in shape and size, one being only 

 93 fi in length, whereas the other measures 528 //, or nearly 6 times the length of 

 the first one. The shorter spicule is sword-shaped with rounded point. In the 

 proximal end it reaches its maximal width, the diameter being about 9/^; af ter 

 which it is tapering evenly towards the tip, being at the same time sHghtly curved. 

 It seems to be hollow throughout the length, presenting along each edge a double 

 contour with distinct transverse striæ. Thus, in optical section it has the aspect of 

 two converging rods, meeting in the end and transversally striated (P. IV fig. 31). 

 The above description applies to the spicula when seen in profile. In a preparation 

 dorso-ventrally compressed, it is squeezed together and presents quite another appear- 

 ance. It then apparently will have its maximal width at the middle, showing a 

 longitudinal thickening which in faet will be nothing but a fold due to the pres- 

 sure (PI. IV fig. 24). The ring-shaped profile of the proximal end of the spicule as 

 seen on the fig. distinctly shows the interior cavity, mentioned above. The longer spi- 

 cule nearly has a uniform width throughout its length, but for a small dilatation in 

 its proximal end. It contains a cavity similar to that of the thicker spicula. In op- 

 tical sections, however, the slender spicula appears as two parallel lines, turning 

 off each other at some distance before the tip and meeting together in the very 

 end of the spicula, — whereas the thicker spicula were seen as two converging 

 rods meeting in the distal end. In other words: The point of the longer spicule 

 most of all resembles a strongly twisted piece of wire (PI. IV fig. 30). When 

 seen under high magnifying power the point of the long spicule looks as if surrounded 

 by a fine membrane, in optical sections resembling a ferrule of a sword (PI. IV fig. 30), 

 or it might be considered somewhat similar to the so-called "cutter" in certain Poly- 

 chæte setæ. When the spicules are at rest and in their natural position in the worm, 

 the tips are almost converging or at any rate placed quite near to one another, 

 whereas for the rest the spicules are diverging and form a distinct angle. In the 

 fig. 24 the shorter spicule is retracted unnaturally far. Most frequently the longer 

 spicule will be seen protruded, stretching out of the anogenital duet with almost half 

 its length. It will then be strongly bent, the protruded distal part at a right 

 angle to the proximal part. The curving takes place somewhat within the anus. The 

 shorter spicule was never found protruded in any case. 



Under high magnifying power both spicules appear to be surrounded by a most 

 pecuhar apparatus which shall now be explained, without laying claim to any com- 

 plete correctness. Especially it is possible that the thing found extends further back or 



