166 C. T. HUDSON ON THE ROTIFERS. 



instance given of an apparent exercise of reasoning faculty in the 

 case of an individual which had caught an object too large to be 

 drawn into its mouth and too rigid to be safely grasped by the disc. 



(25) Stephenoceros — very rare in the neighbourhood of Bristol. 



(26) Bowerbankia. (27) Annelid Larva3. (28) Pedalion, with 

 its male. (29) Diagram of some of the ordinary things found at 

 the sea-side, to show the applicability of the process of illustration 

 to this class of subjects. In the course of his remarks, Dr. Hudson 

 pointed out the great value of dark ground illumination in the 

 examination of Rotifers, and gave some hints as to the means of 

 successfully accomplishing it ; the essential conditions being perfect 

 collimation, accurate focussing, perfectly clean glass slide, cover, 

 &c, not too much water, and the absence of any extraneous matter 

 either above or below the object. With regard to the preparation 

 of his diagrams, he described them as being made of stout 

 " endless ' : brown paper ; the outline of the picture was drawn 

 upon this, and then cut out, and the space filled in again by pasting 

 a piece of tracing cloth over it. The colouring was for the most 

 part done by sticking on pieces of coloured tissue paper, the 

 shading being effected either by additional thicknesses of tissue 

 paper or by a brush ; paints might also be used at discretion to 

 produce effects as required. The cilia were represented by small 

 holes punched out of the cloth or paper with a fine punch about the 

 size of an ordinary pin's head ; and the high lights were produced 

 by cutting through the cloth and covering with tissue paper only. 



