NERVOUS SYSTEM. INVERTEBRATA. 25 



branches, that run in the connectives to neighbouring or 

 distant ganglia. 



The ganglion-cells cover the lateral and ventral surfaces 

 of the neuropile masses of the ventral-chain ganglia ; the 

 connectives occupy the dorsal surface. In each connective 

 there is a giant nerve-tube ; it originates in a large cell on 

 the ventral surface of the cerebral ganglion and runs the 

 whole length of the chain without apparently giving off 

 lateral branches ; it finally divides and passes into the 

 nerves of the tail-fin (uropodites). The giant fibres in 

 their origin and distribution present a striking parallel to 

 Mauthner's fibres in the spinal cord of Fishes, and it has 

 been suggested in both cases that possibly they put the 

 steering and balancing apparatus under the direct control 

 of the brain. 



In the upper specimen the origin and course of the 

 visceral nerves are seen from the left side, indicated by 

 black paper; in the lower the nervous system is shown, as 

 a whole, in its natural position from above. The left eye 

 has been removed to expose the antennary nerves. 



0. C. 1302 i. 



Krieger, Zeits. wiss. Zool., Bd. xxxiii. p. 5^7 (Anat.). 



Allen, Quart. Journ. Micr. Sci., vol. xxxvi. 1894, p. 483, 

 & vol. xxxix. 1896, p. 33 (Histol.). 



Bethe, Arch. f. Phys., Bd.lxviii. 1897, p. 449 (Pliysiol). 



D. 15. A Lobster (Homarus vulgaris), dissected to show from 

 the ventral aspect the cerebral ganglion and ventral chain. 

 The origins of the optic and antennary nerves are shown, 

 also the divergence of the connectives for the passage of 

 the O3sophagus. 



The degree of transverse approximation of the con- 

 nectives in the region of the thorax has been made apparent 

 by the removal of the common neurilemma-sheath, by 

 which they are naturally bound together. v 0. 0. 1301. 



Hunterian. 



D. 16. The cerebral ganglion with the eyes and the principal 

 nerves given off from the ganglion, displayed in situ, from 

 a Lobster (Homarus vulgaris}. O. 0. 1303. Hunterian. 



