NOTES ON BRANCHIOBDELLA. IOI 



During these movements B. instabilia change their shape, the 

 long, slender worm quickly becomes short and broad posteriorly. 

 I had some small clepsine in the same aquarium and was much 

 impressed with the great similarity of movement between the two. 

 This peculiar leech-like movement together with the prominent 

 posterior disk by means of which the animal adheres to the crab 

 so simulates the general external appearance of leeches that it 

 was doubtless one of the reasons for classifying Branchiobdella 

 at first with the hirudineans. 



Moore, '93, first describes these two representatives of Bran- 

 cJiiobdella and reports them only from Watauga Co., North Caro- 

 lina, and Delaware Co., Pa., and so far as I have been able to 

 determine they have not been recorded as occurring farther 

 north than Pennsylvania. The water of Lake Clear is derived 

 almost entirely from springs, but two mountain brooks flow into 

 it, so that the water does not warm up much during the summer. 

 The latter part of July, when the worms were taken, the tem- 

 perature of the water along the shore rarely exceeded 70 F. during 

 the day. When the crayfish having the parasites were placed in 

 a small aquarium the Branchiobdella did not live more than 

 twelve hours although the water was taken directly from the lake 

 and changed once during that time. I am inclined to attribute 

 their death largely to the rise in the temperature of the water as 

 the aquarium was placed in the boat house, which was at least 

 15 to 20 warmer than the water in the lake. 



The animals taken all seemed to be sexually mature, as subse- 

 quent study proved, and were all about the same size. Although 

 I have over fifty specimens of Branchiobdella instabilia there does 

 not seem to be any noticeable variation in their size or appear- 

 ance. 



The biannulation of all but the head segment in B. pnlclicr- 

 rijiia and the first four just back of the head in B. instabilia is 

 very suggestive of leech-like affinities in these forms, which are 

 now generally agreed as being oligochaetes. The coelomic cavity 

 is clearly defined and perfectly divided by dissepiments into a 

 series of cavities. The ccelomic space is encroached upon by the 

 enormously long muscle cells which correspond to the well- 

 known circular and longitudinal muscles of the oligochaetes. 



