642 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Tn Avicula argentea a very interesting condition is noted, there are 

 both ciliated discs (eleutherorhabdic) and organic interfilamentar junctions 

 (tynaptorhabdic). In Anomia aculeata, as in the rare Dimya, the gill- 

 iilaments are not reflected, i.e. they have no ascending portions. 



Ligament of Bivalves.* — 0. M. Eeis has studied this structure 

 with such extraordinary detail and thoroughness that he must surely 

 have finished off the subject. His communication extends over more 

 than a hundred pages, and his summary over sixteen. The ligament 

 is a modification of shell-formation, it includes a non-elastic portion, 

 hardly distinguishable from the periostracum, and an elastic portion, 

 distinctly laminated or layered, traversed usually by calcareous fibres 

 running transverse to the layers. The action of the ligament depends 

 upon its elasticity, the elastic portion is always bent postero-veutrally, 

 the non-elastic portion has no function and is indefinite as to position. 



Artbropoda. 



Eurypterid Remains in Cambrian. | — C. E. Beecher describes 

 Strabops thacheri g. et sp. u. from the Cambrian of Missouri, — an inter- 

 esting discovery as almost the only instance of Eurypterid-remains 

 older than the Upper Silurian. Strabops is nearly related to Eurypterus. 



a. Insecta. 



Interesting Case of Mimicry. | — H. Osborn describes a case dis- 

 covered by C. W. Mally in Cape Town. A Jassid in the group Aco- 

 cephalidre — Cephaletus infumatus Percheron — lives on the twigs of 

 Dovea tectorum Masters on which there are numerous thorn-like abortive 

 bracts. These the insect, which has a long thorn-like frontal process, 

 ''mimics" not only in form, but in colour, size, and position, so that 

 even the eye of the practised entomologist finds it difficult to distinguish 

 animal from plant. 



Metamorphosis of Sisyra. § — Maude H. Anthony gives an account 

 of the metamorphosis of this obscure little fly — one of the Hemerobiidae — 

 which passes its larval existence as a parasite on fresh-water sponges, 

 clinging to their surfaces or descending into the open ostioles, jn'ercing 

 the tissue with its long decurved jaws. The food obtained is so pure 

 that there is no residuum, and at least a fourth of the posterior portion 

 of the stomach is atrophied, leaving no opening from the stomach at that 

 end. Carnivorous habits and piercing mouth-parts are common to other 

 hemerobian larvae, but the decurved position of the mouth-parts and the 

 tracheal gills are peculiar to this insect and Climacia, its nearest ally, 

 which has similar habits. Very remarkable, too, is the silk-secreting 

 apparatus, which is formed from a modification of the Malpighiau tubules, 

 and not, as usual in insects, from the salivary glands. 



The mouth-parts are not in the usual opposed position, but are 

 approximated in pairs to form two sucking-tubes, excessively elongated, 



* Jahresliefte Ver. Nat. Wurtteinberg, lviii. (1902) pp. 179-291 (4 pis.). See 

 Zool. Centralbl., ix. (1902) pp. 573-5. 



t Amer. JourD. Sci., xii. (1901) pp. 364-6 (1 pi.). 



% Psyche, ix. (1902) p. 327. See Zool. Centralbl., ix. (1902) p. 532. 



§ Amer. Nat., xxxvi. (1902) pp. 615-31 (IS tigs.). 



