FISSIPAROUS SPECIES OF TUBICOLAR ANNELID 347 



a spot of y-jVij) ^nd a few granules become visible in their yelk. From 

 this size they gradually increase to the j^iiy inch in diameter, acquiring 

 a well-marked vitellary membrane, and a dark orange-red, very 

 coarsely granular yelk. The germinal vesicle and spot may still be 

 rendered visible by pressure, the former being about -g^jj of an inch' 

 in diameter. 



When those segments of the body in which the genitalia are 

 situated were subjected to moderate pressure, the spermatozoa made 

 their exit at the bases of the pedal tubercules of the male segments,, 

 while the ova, just giving rise to bulgings in a corresponding 

 position, eventually passed out in the same manner. I could not 

 satisfactorily decide, however, whether the apertures by which the 

 generative products passed out were natural or artificial.^ 



Setce and Uiicini of the Pedal Tubercles. — The general form of the 

 pedal tubercles has already been described ; it remains only, 

 therefore, to note more particularly the form of their appendages, 

 whether Setce or Uncini. The Setce (figs. 7, 8) are slender spines, 

 about -gJg- of an inch in length, consisting of a haft and a blade ; the 

 former is about six times the length of the latter, and is rounded, 

 flattened gradually as it passes into the blade, with which it is 

 completely continuous, though at an obtuse angle.^ The blade 

 tapers gradually to its point, and is smooth on one edge, but 

 minutely denticulated upon the other, while delicate striae are 

 continued from the serrations upon the flat face of the blade. 



Such is the structure of those stronger set:e which are directed 

 forwards on each side of the head-lobe. Those of the posterior 

 segments have a similar general structure, but are more delicate. 



The unciiii (figs. 7, 8) are very small, not more than xoVo inch in 

 length ; and it is not easy to make out their exact structure. Each, 

 however, appears to be composed of a short implanted stem, and a 

 blade set upon the end of this, at somewhat less than a right angle,. 

 like the claw of a hammer. The edges of this blade are minutely 

 denticulated. 



Fissiparous multiplication. — It was only a minority of the Protidce 

 which presented the aspect hitherto described ; for the larger number 



1 It should be added that the genital products occupy about fourteen successive segments, 

 of the abdomen, of which the two anterior are seminiferous ; the rest, ovigerous. See Fig. 3. 



^ I am not aware of any annelid in which the setje are really articulated. The statements 

 of Audouin and Milne-Edwards rest, I believe, upon errors of observation, very intelligible, 

 if one considers what microscopes were twenty years ago. How such strange perversions of 

 fact as the figures of annelid setae appended to Dr. Williams's Report on the British Annelida, 

 published in the Transactions of the British Association for 1851 — can have arisen, it is not so 

 easy to comprehend. 



