66 SUMMARY OF CURRENT RESEARCHES RELATING TO 



something better, by fixing the attention of the very few students of 

 our spider-fauna, among whom no such grouping has hitherto been 

 proposed. Moreover, it is hoped that the arrangement may have 

 some interest to naturalists generally as bearing upon the corre- 

 spondence between structtire and economy and the value of habit as a 

 factor in classification." 



An orb-web may be defined as a series of right lines radiating 

 from a common centre, and crossed at intervals by other right lines 

 attached at the point of contact and covered by viscid beads. Orb- 

 webs are divided generally into vertical snares and horizontal snares, 

 according as they are perpendicular to, or parallel with, the plane of 

 the horizon. The vertical snares the author divides into (1) full 

 orbs, (2) sectoral orb, (3) actinic orb, and (4) orb sector; the 

 horizontal snares into (5) plane orb, and (6) domed oi*b. A table 

 of these divisions is given, with sections and subsections, the former 

 being mainly founded upon the character of the snare, as " simple " 

 or " compound," and the latter being for the most part determined by 

 the " hub " (the small open or meshed cii-cle upon which the radii 

 meet), which may be open, meshed, notched, &c. 



Swiss Hydrachnidae.* — Dr. G. Haller gives an account of the 

 Hydrachnid^ found in Switzerland, with descriptions of twelve 

 genera, including one new genus {Forelia, dedicated to Prof. Forel 

 of Merges) and three new species. 



5. Crustacea. 



Homologies of the Crustacean Limb.f — Dr. A. S. Packard, jun., 

 commences by pointing out that, if we make a section of a typical 

 Phyllopod, e. g. Apus, we see that the apparent bulk of the body is 

 mostly due to the large size and nature of the foliaceous appendages ; 

 these have broad attachments, altogether different to the small anal 

 articulations with which we are all familiar in the crayfish. The 

 appendages of Crustacea may be grouped under four heads : they are 

 sensory (pre-oral), masticatory (post-oral), locomotor (thoracic), or 

 natatorial and reproductive (abdominal). In a table the author gives 

 an arrangement of the appendages in the three sub-classes of Tracheata, 

 and the two sub-classes of Branchiata. The antennae of the Hexapoda 

 are looked upon as the homologues of the mandible of the Arachnida, 

 and the first pair of legs of the Merostomata ; the second pair of 

 antennae in the Crustacea as homologous with the mandibles of 

 Hexapods, the " chela " of Arachnids, and the " maxilla " of Myriopods. 



The Cladocerous limb is thought to be intermediate between the 

 Phyllopodous and Ostracodous limbs, and an ascending series may 

 be seen from the Coj^epoda to the Ostracoda, and thence to the 

 Phyllopoda. Hence, as the young of the Copepoda are all nauplii, 

 and also those of the Phyllopoda, it follows that the ancestral form 

 of all the Entomostracous Criistacea, as originally insisted on by 

 F. Miiller, was a nauplius-like animal. The characters of the Decapod 



* MT. Naturforsch. Gesell. Bern., 1882, Abhandl. pp. 18-83 (4 pis.). 

 t Anicr. Nat., xvi. (1882) pp. 785-99 (2 pis.). 



