292 Is Limulus an Arachnid ? [April, 



; of the late Dr. Von Willemoes-Suhm, whose impor- 

 ; have been overlooked by all writers on Limulus. 

 has been called to them through Mr. E. Burgess 

 by Professor Walter Faxon, who has kindly sent us the subjoined 

 extracts from Von Willemoes-Suhm's Letters. 



The first reference by Von Willemoes-Suhm was in the Zeit- 

 schrift fur wissenschaftliche Zoologie, xxrx, 1877, writing from 

 Yeddo under date of May 7, 1875, he says : " I have in the mean- 

 time discovered in the Philippines that the Limulus living there 

 develops from a free-swimming larva, viz., a Nauplius stage, a 

 fact of great significance to the whole doctrine of crustacean de- 

 velopment. The preliminary notice concerning it, which I soon 

 send to the Royal Society, will soon come to your notice. Pack- 

 ard and Dohrn have had to do with an animal which, like the 

 crayfish, has a condensed development." (p. cxxxn.) 



A fuller statement is in a postscript to a letter written aboard 

 the Challenger to Professor Kupffer, dated " Zamboanga, Min- 

 daua, 4 Februar, 1875," printed in " Challenger-Briefe von Ru- 

 dolf von Willemoes-Suhm, Dr. Phil., 1872-1875. Nach dem 

 Tode des Verfasser herausgegeben von seiner Mutter," Leipzig, 

 1877, pp. 157, 158. I am indebted to Professor Faxon for the ex- 

 tract of which I give the following translation : 



" I send you this postscript in order to forward early informa- 

 tion that it has befallen to me to find on the surface of the water 

 here, about five stages of development of Limulus rotundicauda, 

 which does not, like the North American species, according to 

 Packard and Dohrn, directly develop, but passes through a Nau- 

 plius stage, with one, afterwards with three eyes, wholly like 

 a Phyllopod. A tail spine is present, but jointed above, and in 

 this stage shows a parallel with Eurypterus. Packard's mode of 

 development is a condensed one, and as would appear, his as well 

 as Dohrn's and Van Beneden's generalizations on the position of 

 Limulus are throughout untenable, in so far as they remove this 

 from the Phyllopods ( Apus and Branchipns). They rather be- 

 come closely allied through their common Nauplius with three 

 pair of appendages ; and a part of the ' Gigantostraken,' especially 

 the Eurypteridae, should be added to them." 



" As soon as I reach Japan, I hope to also examine the Limu- 

 lus there. The larvae here are unfortunately very rare and 

 difficult to isolate but I have good preparations of the most 

 important stages. I hope to fall in with the northern species." 



