38 



The Rut in Sheep. 



only the anterior half of the creature thus covered, while in 

 others no papilla? could be detected on any portion of the skin. 

 These variations do not seem to mark any difference of species, 

 nor to be indicative of the age of the entozoon ; but to be 

 probably depending on a casting off or shedding of the papillae, 

 as we see in so many other creatures. The epidermic portion 

 of the skin is very thin and transparent, and appears to be 

 homogeneous. It is best examined by stripping off a portion of 

 the integument as a whole, when torn fragments of epidermis 

 will be met with on the edges of the detached piece. The 

 substance of the dermis or true skin appears to be composed of 

 minute granules, arranged in some parts in a linear form 

 both longitudinal and transverse, incorporated with numerous 

 cellules. 



Several of these peculiarities are very well depicted in fig. 3, 

 on the preceding page, which represents a magnified view of 

 the external surface of the entozoon. In addition to the papil- 

 lated skin, the mouth or anterior sucker (a), the ventral or 

 posterior sucker (6), and the so-called intromittent organ or penis 

 (c), are likewise represented. 



Muscular System. — Immediately beneath the integument lies 

 the muscular or contractile tissue, on which the various motions 

 of the entozoon depend. In a creature the parenchyma of 

 whose body is so pulpy as that of the distoma, it is almost im- 

 possible clearly to demonstrate the arrangement of the muscular 

 fibres. It seems, however, that most of them run in a longitudinal 

 direction and others transversely, while some would appear to 

 cross these at angles more or less acute. Towards the mouth 

 the fibres are stronger and more clearly developed, as they also 

 are about the region of the ventral sucker ; their special arrange- 

 ments, however, in regard to these organs will be hereafter 

 considered. 



Aquiferous System. — Traversing the parenchymatous and other 

 structures in every possible direction, immediately beneath the 

 integument, are numerous tubes, exceedingly small in size, form- 

 ing a beautiful rete 9 akin, as is supposed, to the capillary system 

 of the higher order of animals. These tubes have been de- 

 scribed as ending in minute coeca, which they would appear here 

 and there to do, but their continuous connection as well as 

 reticulated arrangement are well seen in flukes rendered trans- 

 parent by immersion in glycerine. They give passage to a 

 colourless fluid, in which float numerous granules. These 

 tubes would seem to be chiefly concerned in nutrition, but 

 whether they have any direct communication or not with the 

 true digestive system we have been unable to determine. Indeed, 

 this is a point in connection with the organism of the distoma on 



