990 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and is especially distinct only in the species with a circlet of hooks 

 on the rostellum. (b) The sucker-nerves result from a proliferation 

 partly of the cerebral mass, partly of the secondary nerves and their 

 commissures, (c) Dorso-ventral or transverse commissures and poly- 

 gonal commissure branches are homologous with the still irregular 

 commissures in the Bothriocephalus scolex or Ligula head. Tho 

 regular disposition of the suckers determines the regular distribution 

 of the commissures. The ten branches from the brain are demon- 

 strable through several proglottides. 



5. The Acanthobothrise form the transition from the Tsenise to the 

 Teirarhynchi. The ten longitudinal nerves have exactly the same 

 course as those in Tsenise, but the central organ and the head-nerves 

 apjn'oach those of the Tetrarhynchi. 



6. Tho commissural branches in the Tetrarliynclius head are 

 directed more towards the centre than in Tsenise. There are two quite 

 distinct commissures, extending between the lateral ganglia. The 

 nerves of the proboscis are in part modified and strengthened acces- 

 sory longitudinal nerves. 



7. In Phyllobothrium and Anthoboth-ium the nervous system is 

 simpler. From a central knot of cells, four strong branches extend 

 upv\ards, leading into the head lobes and branching there. Lateral 

 strands pass into the chain of joints. 



8. The brain varies considerably among Cestodes. In all, well- 

 developed ganglion-cells are most abundant in the middle of the 

 principal commissure. The central position of the ganglionic mass, 

 and the radial disposition of the roots of the longitudinal nerves, 

 results in a symmetry which represents the transition from radial to 

 bilateral. The granular matrix in which nerve-fibres and ganglionic 

 processes usually lose themselves, is not always present. Ganglionic 

 cells seem to occur in all Cestodes. 



9. Nerves with nuclei can be certainly demonstrated in the 

 Cestodes. 



10. The spongy character of the strands is conditioned by 

 several causes. The nervous elements of the network are variously 

 folded under the strong compression of the longitudinal musculature. 

 Owing to their delicacy, they often seem, on longitudinal section, to 

 be united in protoplasmic strands with occasional cross-bridges. 

 The strands are not unfrequently penetrated by muscle-fibres, and 

 surrounding cells insinuate their processes, which also aid in pro- 

 ducing the net-like structure. 



11. In the proglottides lateral branches are occasionally given 

 off from the principal strands. 



New Parasitic Rhabdoccel.* — M. A. Giard describes under the 

 name of Fecampia erythrocephala a new species of Rhabdoccel, which 

 lives for part of its life parasitically on various Decapod Crustacea 

 at Fecamp and Yport. Carcinus msenas in its young stages is most 

 ordinarily infested ; the parasites live in the body-cavity under the 

 digestive tube, and are partly hidden by the liver. It is 1'5 cm. to 

 1*8 cm. long, has a cylindrical body, and is attenuated towards its 



* Comptes Rendus, ciii. (1886) pp. 499-501. 



