1 882.] Is Limulus an Arachnid? 287 



parts of these regions. May this not indicate that certain phys- 

 ical influences have primarily induced the variations which have 

 been developed into perfect adaptations ? 



2. May not heliotropism, or the retarding effect of light upon 

 the formation of tissue, partly explain the greater development of 

 the lower stamens, the shortening of the middle, and the abortion 

 of the upper ; and may it not also explain the upward curving of 

 the styles and lower stamens in these plants ? 



3. May not the mechanical action of the insect have some con- 

 nection with the obliquity of the C. chamcccrista flower, and the 

 divergence of the styles and stamens"? C. chamcccrista is like the 

 typical form turned downward and to one side. 



4. In these plants we have found a lack of bilateral symmetry, 

 and we have found it attended with a regular exchange of sides, 

 and that to accomplish a special purpose. Is this commonly so 

 in plants thus irregular, such as the Cannacece and Zingiberacece ? 



IS LIMULUS AN ARACHNID? 



BY A. S. PACKARD, JR. 



IN an article by Professor E. R. Lankester in the Quarterly 

 Journal of Microscopical Science, for July and October, 1881, 

 entitled '* Limulus an Arachnid," the author, distinguished for his 

 histological and embryological papers especially relating to mol- 

 lusks and Ccelenterates, takes the ground that Limulus, or the 

 horse-shoe or king crab, " is best understood as an aquatic scor- 

 pion, and the scorpion and its allies as terrestrial modifications 

 of the king crab," and on p. 507 he makes the following startling 

 announcement : " That the king crab is as closely related to the 

 scorpion as is the spider has for years been an open secret, which 

 has escaped notice by something like fatality." While appre- 

 ciating the thorough and critical nature of the learned author's 

 work, especially observable in his excellent paper on the structure 

 of Apus, we venture to assert that in regard to the systematic 

 position of Limulus, Professor Lankester has mistaken interest- 

 ing analogies for affinities, and has on quite insufficient and at 

 times wholly hypothetical grounds rashly overlooked the most 

 solid facts, and safe inductions from such facts, and arrived at very 

 forced and it seems to us strange and quite untenable conclusions. 

 At the outset, it will be remembered that Limulus differs from 



