AUTHOR S ABSTRACT OF THIS PAPER ISSUED 

 BT THE BIBLIOGRAPHIC SERVICE, DECEMBER 27 



THE CIRCULATORY SYSTEM AND SEGMENTATION 

 IN .AJRACHNIDA 



ALEXANDER PETRUNKEVITCH 



Yale University 



TWO TEXT FIGURES AND TWO PLATES (SEVEN FIGTJRES) 



The circulatory sj-stem in Arachnida has been made repeat- 

 edly the subject of studies and is fairly well known. Never- 

 theless, several points have escaped observation, partly on 

 account of technical difiiculties, partly because the attention 

 of the investigators was directed toward other aspects of their 

 study. Thus it came to pass that the relation of the circulatory 

 system to the problem of segmentation in arthropods received 

 less attention than it deserves. Indeed, in this respect the cir- 

 culatory system may be more valuable than the nervous system 

 and may, with a certain portion of the alimentary canal, of 

 which I shall speak in a later contribution, help to estabhsh 

 definite homologies within the phylum of arthropods, and thus 

 not only clear the relationships between the various classes 

 belonging to that phylum, but also throw Hght on their phylogeny. 



Many years ago, in the spring of 1905, while on a trip to 

 Jamaica, West Indies, I collected scorpions and spiders, preserv- 

 ing them in the only fluid then obtainable in Jamaica, a mixture 

 of alcohol with ether. The specimens were simply thrown into 

 a jar and left in the fluid, as I did not intend to use them for any 

 anatomical or microscopical study. Quite recently I wanted a 

 few sections through scorpion embryos for class demonstration, 

 so I imbedded and sectioned some quite young scorpions which 

 had been carried by their mother on her back and of which I 

 had many specimens representing stages before and after the 

 first moult. I also took embryos out of the uterus. My sur- 

 prise was great when I found that the fixation of the tissues was 



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