Introduction to Annual Morphology. 23 



Crustacea the nerves have medullary sheaths. When 

 nerves divide, their sheaths attenuate, but the sheath 

 on small branches is thicker than on larger. On very 

 small branches the sheath of Schwann is lost first, then 

 the medullary sheath : then the axis cylinder splits 

 into its component fibrils. 



Nerve fibres begin in uni- or multipolar,* finely granular, 

 nucleated, and nucleolated nerve corpuscles (dilatations of the 

 axis cylinders ?) surrounded by a capsule of connective tissue. 

 Clusters of nerve cells embedded in protoplasm and a copious 

 inter-fibrillar matrix are called ganglia. Nerves end in diffe- 

 rent ways: i. In free ends between epithelial cells (in cornea, 

 Hoyer and Cohnhcim). 2. In pear-shaped bodies (epiglottis, 

 Klein] or pyramids of protoplasm with clear elliptic nuclei 

 (testis, Le/sen'ck), or in branched gland-cells (?}(Pjluger}. 3. In 

 sense organs they end in fusiform or rodlike bodies with non- 

 vibratile blunt processes (gustatory cells of Lwen and Key, 

 the smelling cells of Schultze, sentient cells of rete mucosum, 

 <a, retinal cones, and Cortian rods). 4. In Pacinian cor- 

 puscles, or dilated Imlbs of diverging primitive fascicles sur- 

 rounded by a finely granular mass of protoplasm, and en- 

 closed in dense concentric laminae of connective tissue. f 

 Similar club-shaped bodies without the connective capsule 

 are the end organs of Krause. The corpuscles of Meissner in 

 the sensitive palmar papillae, are furrowed bodies into which 

 a nerve enters and twines round once or twice, rising to its 

 top. 5. In muscle, nerve fibres end by entering the sarco- 

 K-mma in little conical eminences (Doyerian papillae), then 

 i;inc( up into a widomeshed plexus of fine filaments which 

 may end in a plate composed of an upper granular layer and 



i may have many pole-, hut has only one pcripheric branch 



.--times a spiral filament (or 2, 3, or 4 such, as in the Frog) 



winds round the straight periphcric branch --two kinds of these, nervous 



the substance of the corpuscle, fibrous from a basal network, are 



t Bodies hkc / 1 in chains on an axis band, 



;>air!ui between the pyramid and the canal for the tensor 

 '1 as in the mn>toid cells. 



