448 JOURNAL OF THE WASHINGTON ACADEMY OF SCIENCES VOL. 22, NO. 12 



JESC SOS 69 



Fig. 3 d* If. prisliurus, 

 from balsam specimens; 

 stain, acid carmen. Com- 

 pare with Fig. 1. Here the 

 nuclei are brought out more 

 distinctly. The renette and 

 caudal glands may be fol- 

 lowed throughout. Devel- 

 opment of the sperms can 

 be followed; reduction divi- 

 sion is shown at 2. The 

 long gland accessory to the 

 male gonads can be followed 

 from 23 to 33. One of the 

 exceedingly slender spicula 

 is shown, together with its 

 long duplex, nucleated re- 

 tractor muscle. The oblique 

 copulatory muscles of the 

 male extend forward to near 

 the vicinity of 74. The 

 minute but important spin- 

 neret valve is shown at 20. 

 The oesophageal glands 

 shown at 28, may be profit- 

 ably compared with the 

 larger drawings in Fig. 1. 



conical supplementary organs, 19, 

 on the ventral and subventral pos- 

 terior two-fifths of the tail. These 

 are arranged in a sort of ventral 

 row, but the anterior ones are more 

 or less staggered; they are somewhat 

 unequally spaced, being wider apart 

 posteriorly. They give a serrated 

 appearance to the ventral contour of 

 the posterior part of the tail, hence 

 the specific name, pristiurus (saw- 

 tailed). There are also about thirty 

 ventrally submedian short setae, 18, 

 on the front portion of the tail, 

 about fifteen on each subventral 

 line. These two rows extend forward 

 to, and around, the anus, forming 

 there a sort of circlet of inconspic- 

 uous character. These conical sup- 

 plements and setae of the male are 

 special sensory organs; each is supplied with a 

 minute nerve readily demonstrable with seawater- 

 methylene-blue (See Fig. 4). 



The internal male organs. The two slender, 

 straight testes, 7, 63, 70, 76, of about equal length, 

 but the posterior somewhat the longer, are out- 

 stretched in opposite directions, and extend along 

 the middle third of the body, each being about 

 sixteen body-widths long. The ejaculatory duct, 

 17, 59, toward the anus, is one-fifth; the vas 

 deferens, 14, 53, next farther forward and set 



150 



