ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 521 



muscle-pearls, are not free concretions or " depositions from the blood '' 

 (Southwell), but are minute pearls formed of the hypostracum or muscle- 

 attachment substance. They are not the cause of nacreous muscle-pearls, 

 but a phase parallel to them. There is some reason to believe that the 

 origin of muscle-pearls is associated with pathological invaginations or 

 immigrations of the epidermis at the points where the muscle-attachment 

 epithelium passes over into the ordinary outer mantle-epithelium. 



5. Parenchyma pearls (Herdman's cyst pearls) may be formed around 

 grains of sand or other foreign particles, organic granular matter of doubt- 

 ful origin, or bodies composed of varieties of the shell-substance which 

 arise when the normal rhythm of secretion is disturbed (repair substance). 

 A foreign nucleus is probaljly rather exceptional. The ultimate factors 

 which give rise to the epidermal sacs in which pearls are formed have 

 yet to be discovered. Many of them are probably of the same origin as 

 muscle-pearls, except that they arise singly at points where a few muscle 

 fibres are inserted into the shell, instead of in clusters at the regular 

 muscle-insertions. The dark pseudo-nuclei of these pearls, which may 

 easily be mistaken for the remains of parasites, are usually composed of 

 the repair substances. 



Arthropod a. 

 "■■ Insecta. 



Saws of Sawflies.* — F. D. Morice describes in detail the saws or 

 terebrffi of the Chalastogastra. The complex organ consists of five pairs of 

 parts, and is more of a wedge than a saw. It can rasp, scour, and other- 

 wise lacerate, according to peculiarities of armature in particular cases ; 

 but, on the whole, it cleaves its way as a ship's prow through the water, 

 or a ploughshare through the soil. 



Parthenogenesis in "Worker Ants.f — W. C. Crawley gives the details 

 of what seems to be a genuine case of parthenogenesis in Lasms niger, 

 confirming Eeichenbach's experiment, and helping to prove that eggs 

 laid by workers can produce workers and not males. No males were 

 produced. The egg-laying capacity of the workers is not of very long 

 duration, lasting two seasons at most. 



Abnormal Queen Bee.| — J. A. Nelson describes a queen bee with a 

 broadly ovate abdomen, with the three terminal segments strongly bent 

 ventralwards, and with several detailed peculiarities. There was no hint 

 of hermaphroditism, but there were various peculiarities in the reproduc- 

 tive organs, such as the entire absence of the left ovary and its duct. 

 The cell from which the* queen emerged was to all appearance entirely 

 normal. 



Stigmata of Rhynchota. — H. Mammen has made a study of the 

 minute structure of the stigmata in Heteroptera and Homoptera. 



* Trans. Entomol. Soc. London (1911) Part V., pp. cxxviii-clv (7 pis.), 

 t Trans. Entomol. Soc. (1911) pp. 657-63. 



X Proc. Acad. Nat. Sci. Philadelphia, Ixiv. (1912) pp. 3-5 (2 figs.). 

 § Zool. Jahrb., xxxiv. (1912) pp. 120-78 (3 pis. and 22 figs.). 



October 16th, 1912 2 N 



