28 Journal of Comparative Neurology. 



ganglion.^ The central nerve fibers from the diffuse sense-or- 

 gans of a cephalic cirrus can be traced directly through the ax- 

 ial nerve of the cirrus in which they lie into the ganglia at its 

 base and seem to have a definite connection with the cells of 

 the latter structure. 



The central processes from the diffuse sense-organs of the 

 tips of the palps pass into the axial nerve of the palp. Each 

 of the two palp-nerves passes to the anterior projection of the 

 brain which lies on its own side. Each then passes directly to 

 the caudal part of the lateral margin of a palp ganglion — a 

 mass of minute ganglion cells situated in the cephalic half of 

 each side of the brain, — and finally mesad and cephalad into this 

 mass of cells. (See Text-figure 3). 



Retzius ('95) has figured and described a mass oi minute cells— which he 

 calls " vordere Haufen groben Korner," just in front of each anterior angle of 

 the brain, but entirely outside of it. Racovitza ('96) considers that each of 

 these '•Haufen" is composed of two ganglia — " ganglions palpaires et gang- 

 lions antennaires," and that they are in the brain itself. Hamaker ('98) likens 

 the "Haufen" of Retzius to merely the "ganglions antennaires" of Raco- 

 vitza. He evidently doubts the connection of these bodies with the tentacles 

 and considers them equivalent to the " mushroom bodies " of the insect brain, 

 bodies which are supposed to be the center of control of intelligent action. I 

 have not yet had time to make a thorough studjwof the brain itself; but from 



1 A point which, so far as I know, has not been previously noted is that 

 this nerve — the " accessory connective " of Turnbull ('88) — is possibly a com- 

 plete connective — a second circum-cesophageal commissure. From the second 

 cirral ganglion, in which this connective has been described as ending, a nerve 

 which appears to be a continuation of the accessory connective, passes through 

 the first ganglion and, just dorsad of the latter, joins the dorsal border of the 

 circura-CESophageal commissure or primary connective. In the dorsal border of 

 this connective, the nerve in question can be traced for a short distance toward 

 the brain, but finally the sheath separating it from the rest of the connective 

 disappears, although the bundle of fibers seems to retain its original position. 

 Just after this the primary connective gives off its dorsal root from its dorsal bor- 

 der. It may be possible that this dorsal root is simply the nerve from the 

 cirral ganglion. In this case the "accessory connective " would be a complete 

 connective passing from the sub-oesophageal ganglion to the brain. In a re- 

 cent article, Hamaker ('98) notes the nerve connecting the two cirral 

 ganglia, but does not note its further course. He also describes a second, 

 very slender, dorsal root passing from the commissural ganglion into the brain. 

 I am not able to state whether this also appears to be a continuation of the ac- 

 cessory connective. 



