4 University of California Publications. [Zoology 



show such groups of cells related to them ; but the joints which 

 carry aesthetasks similar to those of the female antennae always 

 contain the groups of ganglion cells. 



It is worth noting that with one possible exception no case 

 has been observed in which the so-called tactile bristles are in- 

 nervated, nor has there been any indication that there are nerve 

 cells standing in relation to them. All the ganglion or sensory 

 cells that have stained with methylene blue are related only to 

 the sense-clubs. Thus it does not appear that the tactile bristles 

 on the anterior antennae are innervated as vom Rath claims for 

 all sensory hairs. 



Though the indications in my material are that the bristles on 

 the antennae do not receive nerve fibres as an axial strand, there 

 is good evidence that the furcal bristles of Cyclops contain nerve 

 strands for a considerable portion of their length. This is shown 

 especially well in cases where vom Rath's fluid was used as a 

 fixing agent, followed by pyroligneous acid. Here the two longer 

 and heavier bristles on each furcal ramus have an axial strand 

 which is distinctly fibrillar in character. In the course of this 

 strand there is a nucleus-like body, which may be distant half 

 the length of the bristle from the base, or less. That these bodies 

 are nuclear is strongly indicated by their reaction to haema- 

 toxylin. PL 2, fig. 11, is a drawing from such a preparation; 

 the fibrillar nature of the core is slightly indicated even here, and 

 is much more striking in vom Rath preparations. There may 

 be more than one nucleus in the length of the axial strand though 

 it is usual to find but one. 



It may be well to note that Chun ( '96, p. 92 and PI. 5, fig. 5) 

 found very comparable structures, which he called nerves, in the 

 longer swimming bristles of Cirriped larvae; and to call atten- 

 tion to Kotte's ( :03) claim for axial strands of nerve fibrillae 

 in the highly developed setae of deep sea Euphausias. This is 

 not the place to discuss the significance or character of the struc- 

 ture in Cyclops; indeed it would be difficult to do so. The ap- 

 pearance described occurs so regularly in tissues fixed and 

 stained in different ways that it is hard to believe we are dealing 

 with artefacts. It should be said that this structure has not been 



