[7] NOTES ON ENTOZOA OF MARINE FISHES. 725 



first half-dozen sections the botliria are distinct fr6m the central part, 

 of which they appear to be small auriculate appendages. The position 

 of the bothria at this point is very plainly lateral. The bothria soon 

 become fused with the central part and then lose their distinctive char- 

 acter, appearing simply as deep indentures on the sides of the head. 

 Fig. 10. The diameter of the central core of the head, at the point 

 where the bothria cease to be distinct, measured between the bottoms 

 of the pits, is .26 mm . The diameter through the head at right angles to 

 this is ,49 mm . The breadth of the sections, including the edges of the 

 bothria is .6 mu \ The latter edges are induplicate, if straightened the 

 breadth would be increased ,2 mm . Proceeding towards the base of the 

 head the sections are found to differ gradually the one from the other. 

 The distance between the bottoms of the fossae becomes shorter and 

 shorter, until, at the point where the lobes of the head are widest, the 

 pits are separated from each other by a mere thread .06 to .08 mm diam- 

 eter, Fig. 13. The diameter of the head at right angles to the above, 

 that is, in the direction which answers to the thickness of the head, is 

 .74 mm . The diameter in the latter direction has increased from the apex 

 to this point from .49 mm to .74 mm , while the opposite diameter, that is, 

 the distance through the head from the bottom of one pit to the bottom 

 of the other, has decreased, in the same distance, from ,26 mm to ,06 ,um . 

 The edges of the fossce have, in the mean time, increased in length. In 

 fact they no longer appear as lips of bothria, but rather as prolonga- 

 tions of borders of a bi-lobed head. The inner faces of these prolonga- 

 tions are smooth, as shown by the entire outline of the cross-section, 

 while the outline of the outer faces is deeply crenulate on account of the 

 longitudinal furrows there cut through. The thickness of these pro- 

 longations at base is about ,32 mm ; at the apex, that is, at the margin of 

 a lip of the bothria, about .08 mm . The entire breadth of the head at 

 this point, about the widest part, is, when the lobes are straight, in the 

 neighborhood of 2.6 mm . Transverse sections, for the greater part of the 

 length of the head, bear a close resemblance to the figure eight. 



Towards the base of the head the central part widens quite rapidly. 

 At first this widening is, for the most part, at the expense of the fossre. 

 For example, in a section where the greatest breadth of the head is 2 mm , 

 the distance between the bottoms of the fossae is .6S mm . A little further 

 back the fossae are represented by deep grooves, while the sections are 

 nearly trapezoidal with crenulate outlines. 



In the mean time the aquiferous vessels have made their appearance. 

 A line joining the two main vessels, as seen in section, would be very 

 nearly at right angles to a line joining the deep grooves, which repre- 

 sent the continuation of the fossa3. The sections were carried back of 

 the head a short distance. In the last ones made, the deep emargina- 

 tions at the ends of the section show the position of what further back 

 on the body are the lateral grooves. The aquiferous vessels still occupy 

 the same relative position with reference to these emarginations. 



