370 Mr. A. S. Packard, Juii., on Liiniilus. 



tures in which it departs from the normal Crustacean type, 

 and with some superficial characters in which it resembles the 

 scorpion. The importance of these superficial cliaracters 

 Mr. Lankester exaggerates, and upon them with a number of 

 supposititious, a priori^ pseudo-facts he constructs, by a pro- 

 cess quite the reverse of the inductive method, a new classifi- 

 cation of the Arachnida. 



We will now briefly criticise some points insisted on by 

 Professor Lankester ; and first, on p. 510, as regards the 

 enslieathing of the nervous cord by an actual arterial vessel. 

 This is to be met with in a less marked degree in the insects 

 (Lepidoptera) as well as scorpions. As regards the com- 

 parison of the nervous system of Limulus witli that of the 

 scorpion, the comparison and statement made in our second 

 memoir, which Lankester sets aside, v*ras based on a month's 

 careful study and description of the nervous system, particu- 

 larly the brain of the scorpion, while our author draws his 

 inspiration from Newport's account and figures. The diffe- 

 rences between the brain and thoracic ganglionic mass of the 

 scorpion and that of Limulus are not even correctly stated by 

 our author. The brain of the adult scorpion, as we stated on 

 p. 7 of our second memoir, sends off nerves to the simple 

 eyes and to the first pair of appendages j in Limidus the brain 

 supplies the eyes alone, the first pair of appendages being 

 supplied from the commissures, as in all phyllopod Crustacea. 

 Had Mr. Lankester examined for himself the brain of the 

 scorpion, he would not have given the strangely incorrect 

 account on p. 511. In the first place, the nerves to the first 

 pair of appendages arise from the brain itself, as we have 

 seen and as has been stated by other authors*, and not, as 

 Lankester says, from tiie oesophageal collar. Moreover, as 

 we stated, the brain is situated in the top of the head of the 

 Arachnida, and not on the same plane as the oesophageal 

 collar as in Limulus. In regard to the morphology (not the 

 internal structure) of the brain, Limulus much more nearly 

 approaches Apus and other Phyllopods than the scorpion and 

 other Arachnida. 



In discussing the external anatomy of Linudus, Mr. Lan- 

 kester claims that between the sixth abdominal segment and 



* Newport, whom our author quotes, expressly states that " imme- 

 diately beneath the nerves to the eyes a large nervous trunk passes 

 forwards from the front of the brain on each side to the small prehensile 

 organs {a), which, in the scorpion, are modified antennas." Balfour's 

 embryological observations show that originally the brain of the spider 

 is a double ganglion, the two forming the adult brain ; our embryology of 

 Limulus shows that the brain is from the beginning a single ganglion. 



