836 SCTMMAEY OF CURRENT RESEARCHES RELATING TO 



been able to prove the existence of large salivary glands, and that 

 not only in the terrestrial, but also in the groups that are essentially 

 marine, such as the Idoteidfe and the CymothoidaB ; this discovery is 

 of esj^ecial importance when we remember that, with but rare excep- 

 tions, these glands are only found in laud-forms ; on the other hand, 

 we must remember that in certain Decapod crustaceans small glan- 

 diilar masses, which have given some indications of being salivary in 

 character, have been already observed. Indeed, the author thinks 

 himself justified in extending to the whole group the results which he 

 has found true for the Isopoda. 



With regard to the processes of respiration the author made a 

 number of experiments which resulted in showing him that though 

 there is a very close resemblance in the characters of the organs by 

 which they are effected, there are but few forms that can, without 

 danger, exchange a terrestrial for an aquatic mode of life, or vice versa. 

 Of such we have an example in Ligia, but here, as in all, the air 

 respired must be damp. 



Especial attention may be given to the sympathetic nervous system, 

 the arrangement of which is as yet only incompletely known ; it is 

 much more complex than that of the Decapoda, and the splanchnic 

 system appears to be analogous to that of the recurrent intestinal 

 nerves of Limulus, arising as the nerves do from the hindermost of 

 the nerves of the body ; on the other hand, there is a close resem- 

 blance between the minute structure of the nervous system of the 

 Isopoda and the Decajjoda. 



Lereboullet has already pointed out that the silky secretion 

 formed by the cutaneous glands of certain terrestrial forms, pre- 

 sents a character in which they approach the Arachnida, and 

 M. Milne-Edwards has regarded the so-called white bodies of the 

 opercular gills as rudiments of a tracheal system. By their external 

 form, some Isopods, as for example, Armadillo, approach such 

 Myriopods as Glomeris ; and, taking them in the whole, the Isopoda 

 present a certain number of intermediate characters, by which they 

 may be justly brought into association with vai'ious other groups of 

 Arthropods, and which, at least, give them a very sj)ecial position 

 among the Crustacea. 



Moulting of the Shell in Limulus.* — Dr. A. S. Packard, jun., 

 describes the mode of moulting of the crust or shell of the king-crab 

 (Limulus). 



When found in the course of moulting the shell, the creature 

 " appears as if sj)ewing itself out of itself," as the front edge or 

 frontal doublure splits open around the extreme edge, the narrow 

 rent, easily overlooked in the cast skin, ending (in a half-grown 

 specimen six inches long including the caudal spine) a little over half 

 an inch from the acute hinder edge of the cejihalothoracic shield. 

 Not only is the outer shell cast, including all the spines and hairs, 

 but also the. chitinous lining of the oesophagus and proveutriculus, the 

 proventriculus corresponding to the stomoda^um of the embryo. What 



* Amer. Natural., xvii. (18S3) pp. 1075-G, 



