ENTOZOON-LIKE BODIES. 
155 
as they grow, they become spindle-shaped, and usually one 
end is pointed, while the opposite extremity is more or less 
rounded. In some there are slight projections from different 
parts of the surface, as if there were a tendency to the forma- 
tion of segments and lateral pores. But in the larger ones 
the outline appears perfectly uniform. In all there is a 
distinct investing membrane of a peculiar structure, varying in 
thickness in bodies of different sizes, the outer surface of which 
is in contact with the sarcous tissue (pi. XI., fig. 3), or with the 
sarcolemma, save in the few instances in which the bodies are 
free. Even when the peculiar bodies lie embedded in the 
sarcous tissue, being surrounded on all sides by a thin layer of 
it, the transverse markings of the contractile material are 
perfectly distinct. The masses of germinal matter of the 
affected tissue are not larger than those of adjacent muscular 
fibres. There is no evidence of granular, fatty, amyloid, or 
other form of degeneration; and, whatever these peculiar 
bodies may eventually be proved to be, it is certain that they 
grow within the contractile material, and by their growth 
excite no irritation. The muscular tissue in contact with 
them seems, as it were, slowly to make way for their increased 
bulk, without the occurrence of inflammation or any other 
morbid change. 
Structure of the investing membrane.— Not the least inte- 
resting point in connection with these curious bodies is the 
investing membrane; and it is very desirable to draw the 
attention of helminthologists to its anatomical characters. 
The peculiar structure of the external investment, covering, 
sac, or sheath, will be understood by reference to figs. 4, 5, 
and 6 a , and I shall not here enter into a very minute descrip- 
tion of it. The tissue is transparent, and varies in thickness 
in different parts. It appears to exhibit delicate transverse 
markings, but upon careful examination it is found that these 
are caused by the linear arrangement of minute, hair-like 
fibres. These processes of the investing membrane were 
described by Mr. Rainey in his paper in the Phil. Trans. 
for 1857.* He says they increase in size and distinctness as 
the animal grows larger. “They have not the sharp and 
well-defined outline of true cilia, nor are they pointed like 
setae, or curled like cirri/' In a specimen in my possession, 
however, the bodies in question are certainly pointed, and the 
whole appearance under a power of 1,000 diameters is such as 
would result if the investment consisted of very delicate 
transparent conical hairs, terminating outwards in pointed 
* “ On the Structure and Development of the Cysticercus Cellulosae, as 
found in the Muscles of the Pig.” — Phil. Trans., vol. 147, p. 111. 
M 2 
