774 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the structure of the Euphoberidse, and renders it all the more sur- 

 prising that the penetrating researches of the last thirty-seven years, 

 since the first Carboniferous myriapod was discovered, have not 

 yielded the slightest trace of fossil myriapods below the coal-measures. 

 This discrepancy between fact and hypothesis should, the author 

 considers, stimulate to more searching investigations, particularly of 

 those articulates of the older rocks whose affinities have not been 

 satisfactorily settled. 



7- Arachnida. 



Observations on Scorpions.* — Professor Eay Lankester finds that 

 in the scorpions there exists a similar pair of large coxal glands, 

 having essentially the same structure and position as the coxal glands 

 of Limulus. It does not seem possible to doubt that these are homo- 

 logous structures. Though no external opening has been found as 

 yet, in either the one case or the other, it is possible that such an 

 opening exists. Though glands in a similar position (at the bases of 

 the limbs or jaws) are found in other Arthropoda, there are none known 

 which agree so closely in position and structure with either the coxal 

 glands of Limulus, or of Scorpio, as these do with one another. Possibly 

 such coxal glands are in all cases the modified and isolated repre- 

 sentatives of the complete series of tubular glands (nephrida) found 

 at the base of each leg in the archaic arthropod Peripatus. 



The discovery of the existence of such corresponding organs goes a 

 long way towards confirming the conclusion as to the close affinity of 

 Scorpio and Limulus to which Professor Lankester had been led by 

 the observation of numerous other structural coincidences. 



Professor Lankester also adds a note "j" on the differences in the 

 position of the ganglia of the ventral nerve-cord in three species of 

 scorpion, in which he shows that an important anatomical difference 

 obtains between the scorpions with triangular sternum (Androctoni) 

 and those with pentagonal sternum (Euscorpii, Buthi, &c). Whether 

 the scorpions with bandlike sternum (Telegoni) differ from or agree 

 with either of these types in respect of their nervous system, has yet 

 to be discovered. 



Insecticolous Acari.J — A. Berlese first deals with Hypopus, and 

 confirms the doctrine of Megnin that these animals are heteromorphous 

 nymphs of other Sarcoptidce, and the same seems to be true of Homopus, 

 Trichodactylus, and others ; the pedunculated Uropoda are shown to be 

 nymphs, and it is laid down that no Uropod can be judged to be adult 

 until the presence of the genital operculum has been demonstrated. 

 A number of adult Acari may attach themselves to insects, but, as a 

 general rule, these migratory forms are not adult. Migration would 

 appear to be determined by desiccation and starvation, and insects to 

 be the principal agents in the rapid and extended diffusion of the 

 Acari. 



* Proc. Eoy. Soc, xxxiv. (1882) pp. 95-101 (1 fig.). 



t Ibid., pp. 101-4 (3 figs.). 



X Arch. Ital. de Biol., i. (1882) pp. 279-81. 



