514 JOSEPH STAFFORD, 



at the ends as in the dying animal and when they start again they 

 assume the pointed appearance. I have noticed also one or two 

 single cilia languidly rising and falling while all the rest in the same 

 organ were lying still and extended. These observations seem to in- 

 dicate that each cilium possesses a certain independence and that the 

 pointed appearance of the active ciliary organ is only to be explained 

 from physical causes. 



The shape of each bundle of cilia during activity appears to be 

 a long cone, and its motion a transverse swaying, first at the base 

 where the impulse is given and travelling out towards the end in a 

 wave. Were the organ a flat layer of cilia we should as often see it 

 from the edge as from the broad side. Zacharias speaks of seeing 

 them in profile. They have never given me such an impression, but 

 I have seen organs of different sizes composed of many, a few, or 

 even of single large cilia. Single cilia in slow lashing motion were 

 especially apparent on the walls of some of the bladder-like swellings 

 but so far from their neighboring compound organs that their origin 

 could not be explained as a splitting away from these by the rupture 

 of the vessel, unless the rupture happened in the young animal and 

 they became farther separated with the growth of the vessel. Besides 

 I have sometimes seen them from the i)oint — where the point was 

 directed upwards towards my eye and the base downwards — in which 

 case each organ presented the appearance of a circular disk filled 

 with fine bright punctures. 



The final twigs of the excretory system may be of variable length 

 but measure generally about 45 /<, and can only be followed under 

 the described favorable method of preparation as minute cai)illary 

 tubes with darker walls and bright centres. It must be remembered 

 that these capillaries or their preceding vessels never anastomose with 

 one another and the name must not call up thoughts of the capillary 

 structures of the blood systems of higher animals. The name how- 

 ever, taken in its proper signification, is applicable, but no more 

 applicable to the terminal than to their i)receding branches, except 

 that they may be still smaller than the latter. Near their ends the 

 capillaries expand gradually into the funnel-shaped end organs, some- 

 what isoscels triangular-form as seen from the side, from the base of 

 which project into the lumen of each a flame-like cluster of cilia. In 

 all cases wherever found or from whatever side observed these have 

 the same appearance so that they must be conical in shape. At the 

 base outside of the organ may be seen in favorable cases an elliptical, 



