mVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 735 



immovable and stiff, they appear to consist of a pale homogeneous 

 substance. Having pointed out in detail the structure of the hairs 

 and of the protuberances upon which they rest, Dr. Eisig comes to the 

 conclusion that they are undoubtedly sensory organs : but how are 

 they innervated ? the sensory hairs are connected with rods, the rods 

 with spindle-shaped bodies, and these with granular ones ; between 

 these last and the ganglionic cells of the central cord there are many 

 points of resemblance, although the granules are without a neurilemma 

 and without those unipolar peripheral cells which are found in the 

 cord. As to the nerve, it is curious to observe that there passes into 

 the protuberance a band of matter which, at first sight, is easily taken 

 for the innervator, but which is really a muscle, for which we can 

 easily find a function when we note that the sensory hairs are capable 

 of being protruded and retracted. The true nerves arise from the 

 ventral cord ; three, or rarely four, being given off to either side from 

 the ganglia ; passing through the musculature of the trunk they 

 ramify in the integument, or, reaching as far as the gill, divide into 

 two strong branches, of which one goes to the gill and one towards 

 the sensory protuberance ; the observations, however, of our author 

 do not allow him to speak definitely as to the innervation of the 

 protuberances. 



The remark just made will be found to apply also to the nerves of 

 the lateral organs of the thorax ; as to the pores of these organs, which 

 are elliptical or rounded, and quite evident, no passage could be dis- 

 covered by which they were connected with the perivisceral cavity of 

 the animal ; carefully examining them, Dr. Eisig one day saw a 

 rounded protuberance project from one of the clefts ; this was pro- 

 vided with stiff hairs altogether similar to those already observed in 

 the abdominal region. The whole matter was henceforward clear ; here 

 as in the abdomen there were sensory organs, but here they were 

 ordinarily hidden in cavities formed for their reception ; the pro- 

 tective apparatus was carried a step further in the thorax than in the 

 abdomen. The rounded protuberances are of the same form, though 

 somewhat smaller, and the sensory hairs are exactly similar. 



Leaving these, which are truly segmental organs, we deal with 

 the goblet-shaped organs, which are irregularly scattered over the 

 cephalic lobes, the thorax, and the proboscis ; those on the first- 

 named structm-e are set around its whole circumference, and in great 

 numbers ; rounded or conical in form, they are only of about one- 

 tenth the size of the organs already described as existing on the pro- 

 boscis ; the sensory hairs are not so numerous and do not diminish in 

 size towards their free end, as do those already noted, which are also 

 about ten times as long ; no observations could be made as to their 

 structure or as to the supply of nerves to them. The goblet-shaped 

 organs of the thorax, which are very difficult to make out, are placed 

 in greatest number around the mouth ; very similar to those of the 

 cephalic lobes, they appear to be innervated from the ventral cord as 

 well as from the oesophageal ring. Similar organs are found in some 

 hundreds on the proboscis. 



Bearing in mind the metameric arrangement of the lateral organs 



3 c 2 



