1871.] WOODWAED — XIPHOSTJRA. 55 



of this last suggestion ; but before doiug so it will be desirable 

 to record Dr. Dohrn's views.] 



It is to be regretted that Dr. Anton Dohrn (who has paid so 

 much careful attention to the embryology of the Arthropoda, and 

 whose valuable contributions on this subject have already appeared in 

 the 'Jenaische Zeitschrift,' and are no doubt well known), had 

 only specimens preserved in spirits for examination, which prevented 

 him from fully completing his researches. He, however, deserves 

 our best thanks for what he has accomplished with the materials at 

 his disposal. 



Having already described the larval stages. I will pass at once to 

 the conclusions he has arrived at as to the position of Limulus with 

 regard to the other Crustacea. 



Whether TAmulus does or does not descend from a Nauplius, Dr. 

 Dohrn considers that at present we have no knowledge of a Nau- 

 plius-stage in that genus, any more than in the Trilobita ; but the 

 subsequent stages agree with such forms as Trinudeus and Sao, in 

 the gradual development of the young from a form having a simple 

 cephaKc and caudal plate to the adult stage in which numerous in- 

 termediate body-rings have been added. 



Dr. Dohrn further concludes that Limuhis cannot be retained 

 among the Crustacea, for two reasons : — 



1st. Because of the presence of onl'i/ one pair of eoetremities 

 which receive their nerve-system from the supracesophageal gan- 

 glion *. 



2ndly. From the position and form of the under lip. 



1. Bearing in mind that all Crustacea have two pairs of antennae 

 receiving nerves from the supracesophageal ganglion, thus distin- 

 guishing them from the spiders, Myriopoda, and insects, it is (says 

 Dr. Dohrn) imj)ossible to ignore that the presence of only one pair 

 of extremities (the antennules) in Limulus so supplied with nerves 

 separates it from the Crustacea. And, further, to which of the two 

 pairs of antennae, and therefore to which of the two anterior pairs 

 of extremities, in Nauplius does this first pair in Limulus corre- 

 spond ? And this question we must leave entirely unanswered, as 

 we have at least hitherto been unable to detect any trace of a rudi- 

 mentary second pair either before or behind this first pair." 



Dr. Dohrn therefore concludes that Limulus cannot be retained 

 with the Crustacea, but must be classed with spiders and insects 

 which have only one pair of antennae. 



2. "With regard to the under lip (metastoma). Dr. Dohrn says that 

 in all the Crustacea it is a fold of the germinal membrane behind 

 the mouth. It is found on a level with the mandibles, or sometimes 

 even in front of them. In Limulus the under lip is behind the sixth 

 pair of appendages, and is divided into two parts. 



This led Dr. Dohrn to suspect that it might prove to be really a 

 seventh pair of appendages ; but this point he has been unable to 

 clear up ; for, owing to the fact of his specimens having been in 



* This was first pointed out by Van der Hoeven, in his ' Eecherches sui' I'His- 

 toire Naturelle et TAnatomie des Limules,' 1838. 



