ox TRACHEAN ARACHNIDA. 525 



duct from the crabs to plialangium, we might believe, that 

 nature, in subtracting from the Crustacea their anterior 

 organs, and replacing their tail by an abdomen, thus con- 

 verted them into arachnida. But, admitting this hypothesis, 

 it would still be necessary to pass from the nymphons to the 

 araneides, or to the arachnida called pedipalpi, and it would 

 not be very easy to explain the mode adopted by nature in 

 operating this new transformation. 



As the interior organization of the pycnogonides is unknown, 

 it is not possible to determine the place which these singular 

 animals should occupy in the natural series of created beings. 

 Nevertheless, as they appear to have, in spite of some ano- 

 malies, great relations with clielifer and plialangium, affinities 

 which had already been remarked by celebrated naturalists ; 

 — as the body of many trachean arachnida also presents an 

 anterior articulation, supporting analogous mandibles and 

 palpi ; — as the tubular sucker of the pycnogonides may be 

 nothing but an union of jaws and under lip prolonged and 

 cemented ; — as the absence of composite eyes, and the exist- 

 ence of a tubercle supporting the simple eyes confirm these 

 relations ; — as the feet of the pycnogonides are composed of 

 nine articulations, a character for which we should seek in 

 vain in the Crustacea, but which we shall find in several of these 

 arachnida ; — as in giving to the pycnogonides feet as long, and 

 a linear form adapted to their habits, Nature has been obliged 

 to extend their thorax to the prejudice of their abdomen, which 

 is here represented by a small articulation in the form of a 

 tail ; — M. Latreille was originally determined to place these 

 animals between the pseudo-scorpions, and the phalangia. 

 In his work called " General Considerations on the Natural 

 Order of Crustacea, Arachnida, and Insects," the pycnogonides 

 alone form an order, which unites the parasite insects, such 

 as the pediculi and ricini, to the acerated, or arachnida. 



The nymphons are distinguished from the pycnogona by 



