22 6 DESCRIPTIONS OF PREPARATIONS. 



continuously into deeper strata. There is a thin superficial layer of longitudinal 

 muscles and two deeper layers, an outer of longitudinal and an inner of circular 

 fibres, as well as a system of dorso-ventral fibres. The deep longitudinal and circular 

 layers surround a nucleus or core of connective tissue which lodges the generative 

 organs, the longitudinal excretory canals, and longitudinal nerves. 



In Taenia lineata the cuticula has the same structure as in Solenophoms. 

 There is a similar matrix which is finely granular. It contains large granular, 

 oval, round or amoeboid cells, small fusiform or stellate cells, and scattered nuclei 

 with or without traces of surrounding protoplasm. Tubular or vasiform spaces 

 filled by a granular material lie immediately beneath the cuticula : they sometimes 

 occur empty. There is also a layer of vertically spindle-shaped sub-cuticular cells 

 which give origin to (?) the cuticula. They lose their individuality if the specimen 

 is preserved only in alcohol. The deep longitudinal muscle-fibres are grouped 

 in bundles and retain no trace of their formative cells, as do the dorso-ventral and 

 circular muscle-fibres (Hamann). T. serrata has not been investigated by modern 

 methods with reference to these points. The term ' parenchyma ' is often used 

 in speaking of the connective tissue substance of Cestoda. It is better discarded 

 as the tissue in question is not cellular in structure. 



The nervous system of T. serrata has been carefully investigated by Niemiec. 

 It consists, as in some other Taeniae, of the following parts. A nerve-ring lies 

 a little below the base of the rostellum. It gives off nerves to the muscles of 

 the hooks, and contains eight slight ganglionic enlargements from each of which 

 originates a stoutish nerve passing backwards. Two pairs of these nerves (A, A : 

 A, A\ situated at opposite extremities of the same diameter of the ring, unite 

 each with one of the two lateral principal ganglia. The other two pairs (B, B : B, B) 

 unite with the secondary transverse commissure and the polygonal commissures 

 (infra]. The two lateral principal ganglia are connected by a primary transverse 

 commissure in the middle of which is a voluminous central ganglion. This 

 ganglion gives origin to a slender secondary transverse commissure which lies 

 at right angles to the primary transverse commissure and forks at either end. 

 Each branch of the two "forks unites with one of the nerves B, B, &c. supra, and 

 with the superior polygonal commissure. The lateral principal ganglia and the 

 nerves J?, B, &c., are united by two ring-like polygonal commissures, one superior, 

 the other inferior. The points of union of the nerves B, B, &c., with the secondary 

 transverse and the polygonal commissures are swollen and form secondary ganglia, 

 from which, as well as from the lateral principal ganglia, nerves are given off to the 

 suckers 



The nerves B, B, &c., are continued backwards through all the joints as 

 slender filaments, two on each surface. Three longitudinal lateral nerves, a median 

 stout nerve with a slender nerve on either side, extend backwards in a similar 

 manner, and lie to the outer side of the longitudinal excretory trunks. They are 

 said to degenerate in the ripe joints by Hamann. It is possible that branches 

 may originate in some instances from the lateral nerves. Riehm states that they 

 possess a swelling close to the posterior margin of each joint in Dipylidium 

 pectinatum (=T. pectinata in part) of the Rabbit from which nerves pass both 

 inwards and outwards. Similar swellings exist in Ligula and Schistocephalus (Kiess- 

 ling). Their ganglionic nature is by no means certain. 



