308 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
j3. Myriopoda. 
Poison-glands of Scolopendra.* — M. 0. Duboscq distinguishes the 
three pairs of so-called salivary glands, which have no connection 
with the oesophagus, from the poison-gland which is entirely within the 
poison-claw, between the external insertions of its adductor muscles. 
Numerous glandular tubes radiating around a chitinous excretory canal 
are compressed by a network of striped muscle-fibres. The gland arises 
as an invagination of the skin ; the glandular tubes are modified hypo- 
dermic glands. 
The limpid homogeneous venom, of acid reaction, seems not to act 
except on Arthropods and Vertebrates, and at most very slightly on 
Fishes and Reptiles. On Arthropods it acts with variable virulence on 
the nervous system ; on man and higher Vertebrates its effect is local. 
S. Arachnida. 
Phylogeny of Arachnida.| — Herr J. Wagner begins with a discus- 
sion of the systematic position of Acarina. In Ixodes , the Malpighian 
tubules have an endodermic origin, and are only secondarily connected 
with the rectum. Moreover, in no larval stage of Ixodes is there any 
trace of tracheae. 
Wagner holds fast to the idea that the ancestral form had no tracheae 
opening in the cephalothorax. He believes that gill-books, like those of 
Limulus , gave origin to lung-sacs, and these to Arachnid tracheae. The 
cephalothoracic tracheae of certain Arachnids (e. g. Solifugae) are regarded 
as not directly homologous with the tracheae of other Tracheata. They 
are derivatives of skin-glands. 
The Arachnids split into two groups. In the one the tracheae de- 
veloped greatly, the lung-sacs (modified gills) remained only in part, or 
disappeared wholly ; in the other the skin-glands modified into tracheae 
degenerated, and the lung-sacs increased. 
Wagner thinks it likely that the so-called Malpighian tubules of all 
Arachnids are endodermic ; they are only analogous with those of 
Insects and Myriopods. 
The anatomy of the hypothetical Protarachnon is described at length. 
The ancestor of the Arachnoidea was a Perijpatus-like terrestrial animal. 
From the primitive Crustacea the Crustacea and Trilobites developed ; 
Protarachnon and the Gigantostraca represent a side-twig of the latter. 
Origin and Evolution of Web-spinning in Spiders.^ — Mr. R. I. 
Pocock calls attention to Dr. McCook’s chapter on the genesis of snares, 
in which he thinks that the author succeeds in leaving his readers com- 
pletely in doubt as to whether or no he intends one or all of his attempts 
at tracing the genesis of snares to represent what has actually occurred 
in the course of nature. Mr. Pocock points out that silk threads are 
fabricated by two allied groups of animals. In one of these, the Book- 
Scorpions or Chelifers, the presence of silk-glands has long been known ; 
in the other, the Phrynidse, their existence is now for the first time, it is 
believed, pointed out. One of the chief points of interest in this dis- 
* Arch. Zool. Exper., ii. (1894) pp. 575-82 (5 figs.), 
f Jenaische Zeitschr. f. Naturwiss., xxix. (1894) pp. 123-56. 
t Nature, li. (1895) pp. 417-20. 
