NERVOUS AND EXCBETOET OEGANS. 679 



form of a small drop. ^ One is at the first glance perhaps inclined to 

 regard these structures as forming an absorption-apparatus, but the im- 

 possibility of tracing their contents into the body-parenchyma leads to 

 the supposition that they are structures of a glandular nature, such as 

 occur with more or less frequency in other flat-worms. Their absence 

 in the segmented body, and the fact that they have not been as yet 

 detected among other Cestodes, can hardly be urged as an argument 

 against the above interpretation. They serve, perhaps, for the secre- 

 tion of a mucus or even viscid substance, which facilitates the 

 attachment of the worm. 



The Two Nerve Cords are seen through the head with no less 

 distinctness than the muscle-fibres. They are found at that region 

 where the middle portion passes out into the side, in a position which 

 corresponds topographically to the lateral margins of the jointed body, 

 and which is especially marked in the head, since the sagittal and 

 diagonal muscle-fibres which are attached to the internal surface of 

 the grooves leave a free triangular space at this point (Kg. 355). 

 The nerve strands are seen as two roundish or kidney-shaped spots of 

 granular appearance, which gradually approach one another towards 

 the anterior end of the head, and are finally united in a loop by a 

 transverse connective. 



Internally, the nerve strands are accompanied by a longitudinal 

 vessel, the cross section of which can be traced throughout the head, 

 even far forward. Besides this, there may be observed in Bothrio- 

 cephalus latus a number of fine vessels which extend below the 

 subcuticular layer of cells, and are sometimes united to each other 

 by a lateral branch. 



The Excretory Apparatus of the Bothriocephalidse has, as has been 

 already noted (p. 301) by no means the well-known rope-ladder 

 disposition exhibited by the Tseniadae. Not only do the lateral stems 

 (except in, the head) exhibit a reticulated disposition, the result of 

 repeated division and anastomosis, but these deeper canals are 

 associated with a superficial system of fine vessels, which also form a 

 connected network, and are distributed over the whole body. The 

 opinion was formerly held that this fine network represented the 

 proper secretory surface of the apparatus, and to this I myself 

 formerly inclined, but the researches of Pinter^ and Fraiponf* have 



' I describe these structures from a preparation given to me by Braun, which was 

 made from the head of a Bothriocephalus four days old, from the alimentary canal of a 

 cat. Braun also found these bodies "of doiibtful import" in the B. latus of the dog 

 ("Zur Entwicklungsgesch. d. breiten Bandwurmes," Tab. ii., Fig. 16, p. 55). 



^ "Unters. iib. d. Bau d. Bandwurmkorpers, " Arb. zool. Inst. Wien, Bd. iv., 1880. 



' "Rech. s. I'appareil excrfteur des Trematodes et des Cestodes," .ireAiii. d. Biol., 

 t. i. and ii., 1880 and 1881. 



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