290 Mr. F. E. Beddard on the possible Origin 



gical period from the Upper Silurian strata to the Miocene 

 inclusively. 



Whether this non-existence of the Horny Sponges must be 

 left for further investigation to verify or whether it can be 

 explained by deferred development, that is to the present era, 

 or in any other way, I will not go further here than the fact 

 that the Horny Sponges are by far the most abundant at the 

 present day and yet have no fossil representative. 



XXXVIII. — On the possible Origin of the MalpighianTubules 

 in the Arthropoda. By Feank E. Beddard, M.A., 

 F.Z.S. 



Theee are two sets of structures in the Arthropoda which 

 have been proved to possess a renal function and which have 

 been regarded as possibly equivalent to the nephridia of 

 worms. 



The " green glands " of the Crustacea are commonly 

 regarded as nephridia, and researches now in progress will, I 

 believe, establish the nephridial nature of these organs upon 

 a very tirm basis of fact. 



Among the Arthropoda another class of renal organs exists 

 in the so-called Malpighian caica. These occur in a few 

 Crustacea, e. g. the Amphipoda (Spencer, " The Urinary 

 Organs of the Amphipoda," Quart. Journ. Micr. Sci. xxv. 

 1885), and in Tracheata; in the latter group they consist of 

 a variable number of glandular ca^ca which grow out from 

 the proctodeum ; in the Amphipoda, on the contrary, Spen- 

 cer finds reasons for believing that the tubes in question are 

 diverticula of the mesenteron. 



The only known Arthropod with unmistakable nephridia, 

 paired and metamerically arranged, is Peripatus. The exist- 

 ence of these organs was originally pointed out by Balfour 

 {" On some Points in the Anatomy of Peripatus capensis^' 

 Quart. Journ. Micr. Sci. xx. 1880), and has been since care- 

 fully studied from the developmental as well as from the 

 structural point of view by Sedgwick (" A Monograph of the 

 Development of Pertprtfwi' ca^je/i6«s," Stud. Morph. Lab. Cam- 

 bridge, vol. iv. pt. i.). Lankester had previously pointed out 

 that the " coxal glands " of Limulus were in all probability 

 to be regarded as modified nephridia, and this position is 

 strongly supported by Sedgwick's results. So far as our 

 present knowledge goes it may be safely assumed that the 



