372 Mr. A. S. Packard, Jun., on Limuliis. 



In like raanner he feels compelled to offer a new interpre- 

 tation of the scattered, individual, simple eyes of the scorpion, 

 and attempts to show that after all they are compound eyes, 

 like those of Li/mdus, with the difference that in Scorjno they 

 are " in a less compact form." Now the compound eye of 

 Liniulus, like that of the lobster or any other Crustacean or 

 insect, possesses a common basally undivided retina, in Lt- 

 mulus a common undivided outer cornea, while the two simple 

 eyes in LimuJus have each a separate cornea, a separate retina, 

 and each ocellus is supplied by a separate nerve arising inde- 

 pendently from the brain. 



In like manner our author labours to diminish the import- 

 ance of the differences between the cephalothoracic appendages 

 of the Arachnida and those of Litnuhis. 



Professor Lankester then ventures, we think somewhat 

 hastily, to homologize the first pair of abdominal appendages 

 of Limuhis with a little triangular median sternite in the 

 scorpion. Then he fancifully homologizes the comb-like 

 organs of the scorpion with the second pair of abdominal legs 

 of Limulus, and also homologizes the respiratory lamellas 

 with the " lamelliform teeth of the scorpion's comb-like 

 organs." The author further seriously attempts to homolo- 

 gize the four pairs of stigmata of the scorpion with the four 

 last pairs of biramous respiratory feet of Liriudus. On the 

 same principle the stigmata of any insect are the homologues 

 of its legs. What will Mr. Lankester do with the gill-plates 

 of the Eurypterida, which are not arranged, according to 

 Woodward, like those of Limulus, but are placed like the 

 teeth of a rake ? 



Another surprise is added to the already long list by Mr. 

 Lankester's discovery (of which he makes great account) of 

 what he calls " parabranchial stigmata " in Limulus. He 

 places them on the " sternal area of the segments ;" but his 

 statements on the succeeding page and his figures plainly 

 show that these little muscular pits are situated at the base of 

 the biramous abdominal legs. Is there an instance in nature 

 of stiOTiata being borne on the les:s? Is there the slio'htest 

 possible reason for regarding these pits as stigmata? We 

 are then treated to a long series of suppositions, accompanied 

 by a series of elaborate hypothetical lithographic drawings, 

 designed to '' illustrate the hypothesis as to the derivation of 

 the lamelliferous appendages of Limuhis and Scorjno from a 

 common ancestral form." The late appearance of the lamellae 

 on the leet of the embryo Limulus should teach any naturalist 

 of sound judgment that they are most probably very s])ecial 

 and late differentiations of the appendages. Besides this. 



