ii8 



GENERAL AND SPECIAL CUTANEOUS SENSE ORGANS. 



in which is located the small nucleus, may be finely granular, staining a dark 

 gray or bluish-black in von Rath's fluid. (Fig. 88.) 



Each slime bud contains a single ganglionic or sensory cell, distinguished 

 from all the others by its large size, dark, finely granular protoplasm and indis- 

 tinct outline. This cell appears to be larger and more distinct in the mandibular 

 slime buds than it is in the olfactory buds. 



Between the outer ends of the slime cells there are minute, rod-like bodies 

 with a dilatation at their inner ends. They have the appearance, under some 

 conditions, of being minute sensory cells, but I have not been able to fully satisfy 

 myself that such is the case. In von Rath's fluid, they become very black, 

 and in some cases hair- like processes appear to project from them into the cavity 

 of the slime bud, where they unite to form a small star-like body. (Fig. 85, D.) 



In some cases, the buds are greatly distended and the cells appear nearly 





Fig, 87. — A cluster of ganglion cells terminating in a sub-dermal plexus of anastomosing fibers; from the soft skin 



between the joints of the endopodites of the branchial appendages of a young Limulus. Methylene blue. 

 Fig. 88. — Two slime buds grom the olfactory region of an adult Limulus — von Rath's prepration. a. Groups of cells 

 of unknown significance; c.c, central coagulum resting on hair- like projections. 



colorless and empty, as though after a certain period of activity they were about 

 to degenerate. 



New slime buds, that have arisen de novo from the indiflferent ectoderm, 

 or by the division of the existing buds, appear in the older stages. 



5. In the vertebrates, there is a similar association of sensory and mucous 

 cells in the lateral line organs. For a long time it was assumed that the lateral 

 line canals were primarily slime producing organs, and nothing more. When 

 the sense organs in the canals were discovered, the associated mucous cells were 

 apparently forgotten. 



In the lower vertebrates, the typical taste organs form small clusters of sensory 

 cells, resembling in structure and innervation the taste organs and the flabellar 

 organs in Limulus. (Fig. 85, E.) The typical lateral line organs, or neuromasts, 

 consist of short, hair-bearing sense cells, united with longer so-called "supporting," 

 or indifferent cells, which may or may not secrete mucous (iMaurer). Thisassocia- 



