292 JAMES RANKIN, 



them ''ils font partie du nerf et ne prennent pas la valeur de cellules; 

 il n'est du moins pas possible d'y distinguer un nucleus ou un proto- 

 plasma granuleux". The general arrangement of the caudal ganglia 

 in 0. dioica I have shown in Fig. 3, PI. 18, which was drawn from 

 a living specimen. I have not found a system of paired caudal nerves 

 in 0. dioica ; nerve twigs are very irregular in their occurrence, l)iit 

 when they are jjresent their origin agrees with that recorded for the 

 caudal nerves of other species, viz., except in the case of the large 

 caudal ganglion, they arise from the nerve cord itself and not from 

 the nerve corpuscles. In some instances they are given otî by the 

 nerve cord at a point where no nerve cells are found. The nerve 

 cord in 0. cophocerca appears to be stouter than in 0. dioica. The 

 distribution of the caudal ganglia in F. furcata is shown in Fig. 1, 

 PI. 18. In the nerve corpuscles of F. furcata I have only been able 

 to find a deeply staining nucleus; I have not in any case observed 

 a nucleolus. See Fig. 8, PI. 18. The number of the ganglia I find 

 to be in accordance with Skeligek's statement. It will be seen that 

 ganglia in both 0. dioica and F. furcata are very irregularly distri- 

 buted. There is, however, in both a notable agreement in the relative 

 position of the corresponding ganglia in different individuals. 



The muscles of the tail are of peculiar structure. As has lieen 

 pointed out by previous observers the fibres are transversely striated 

 and have no sarcolemma. Immediately underneath the tesselated 

 epithelium of the tail, in the region occupied by the musculature, is 

 a layer of granular protoi)lasm l)elonging to the muscle fibres. This 

 layer is not divided up longitudinally in agreement with the more 

 deeply placetl fil)res, but is apparently continuous from side ti» side 

 and from end to end of the muscle layer. In some of my longi- 

 tudinal sections, however, it seems to be atlected to some extent by 

 the transverse striation of the fibres. The mother cells of the muscu- 

 lature have an oval or rounded nucleus, but this appears to be altered 

 in a peculiar fashion after the fibres have made their appearance. In 

 the tail of F. furcata. Fig. 1, PI. 18, are seen curions reticulations 

 which lie in the granular protoplasm external to the fil)rous part of 

 the musculature. They are present in both muscle bands, but the 

 reticulations of the opposite sides do not always coincide in position. 

 A reticulation of one side of the tail may be jjlaced in front of (»r 

 behind the corresymnding reticulation of llie opposite side in the 

 anterior part, but nmch more markedly in the posterior part where 

 regular arrangement is altogether aw anting. These reticulations present 



