April. 1912. 



KNOWLMDGi;. 



161 



BORING BIVALVES. — For a long time there have been 

 two theories in the field with regard to the method by which 

 Phol.ids and other bivalves bore through rocks. .-Vccording 

 to one theory the boring is at least partly due to an acid 

 secretion; according to another theory it is mainly accom- 

 plished by mechanical means. B. Lindsay has studied 

 Xirpluica iPholas) crispata and Saxicai'a nifiosa, at St. 

 .•\ndrcws, and comes to the conclusion that the boring is in 

 these cases entirely mechanical. The Zirphnca works in 

 two wa>s — sucking and scraping ; " it might be described as 

 a combination of a nutmcg-gratcr and a vacuum-cleaner." 

 The foot is extruded : a wide gap appears between the toot 

 and the mantle ; the mantle becomes fully extruded, and then 

 rotatory movements begin. The shells consist of aragonite — 

 h.itder than the usual calcite — and this must help in the boring. 



dischargh: of spermato-?oa in fresh- 

 water MfSSEL. — Oswald H. Latter gives an account of 

 this process as he saw it in May of last year. A specimen of 

 L'liio pictoriiin emitted from the exhalant aperture a fine 

 double stream of milky substance, which rose nearly to the 

 surface of the water and then fell as a diffused cloud. The 

 whole of the wafer in the aquarium became cloudy and the 

 emission continued for some hours. It appeared to be under 

 control, for a slight shaking of the floor was followed by a 

 cessation of the streams though the ordinary exhalant current 



of water appeared to continue without interruption. The 

 liberated material consisted of myriads of sperm-balls, revolving 

 and swimming like Volvox. and finally breaking up into the 

 component spermatozoa which exhibited astonishing activity, 

 sustained below a cover-slip for seven hours after liberation. 



THEORY OF GALLS.— Jules Cotte makes some very 

 interesting remarks on the origin of " zocicecidia"; that is to 

 say. galls made by animals. He points out that there is often 

 a striking structural resemblance between the animal-made 

 gall and the plant-made gall ; that animals far apart from one 

 another seem able to make very similar galls ; that the same 

 animal produces very diverse galls : that an animal which 

 causes galls at one place or at one season may be inoffensive 

 at another : that there is sometimes a puzzling disproportion 

 between the dimensions of the gall and the number of alleged 

 producers: that some galls continue to grow after the parasites 

 have disappeared, and that others are formed before the 

 ovum of the parasite has been hatched. All this leads up to 

 the theory that many so-called animal-made galls are due to 

 moulds or bacteria or the like introduced by the animal. The 

 insect or mite is a carrier of a vegetable infection, and in 

 many cases the zoocecidia are demonstrably associated with 

 fungoid growth. Cotte does not deny that there may be true 

 zoocecidia, but he thinks that many are more accurately 

 described as myco-zoiicecidia or phy to- zoocecidia. 



SOL.AR l)ISTrRl!.\XCES DUKIXC I- I-.T-Rr ARV, 1912. 

 Hv FRANK c. di:xxi:tt. 



Fkbruarv has yielded a much better proportion of dates 

 when telescopic scrutiny of the Sun was possible than either 

 of the two previous months. Only on three days (8th, lith, 

 and 16th) did he escape observation. The central meridian 

 at noon on February 1st was 108' 45'. 



No spots were obser\-ed during the month, though there 

 were some faculic disturbances as shown on the diagram. 



On February 2nd and 3rd. a group within the eastern limb 

 occupied the area between longitudes 27° and J 7°, and south 

 latitude y and 6°. 



On the 17th and ISth a facula within the eastern limb was 

 situated at longitude 180', south latitude 9 . 



On the 24th some faculae near the western limb must have 

 been about longitude 245^, and near to the ecjuator. but were 

 not measured. Also on the 24th and 25th a faculic disturbance 

 was noted within the eastern limb, a little over 10° south 

 latitude and near longitude 88". 



On the 27th a small facula was situated at longitude 205°. 

 north latitude 20°. and so near the north-western limb. A 

 larger and paler disturbance, containing a dull patch near its 

 eastern end. was also approaching the western limb, and 



situated between longitudes 90° and 200. south latitude 6" to S". 



On the 29th a facula. doubtless that seen on the 17th and 

 18th, was approaching the western limb in south latitude. 



Mr. E. W. Maunder, writing at the desire of the Astronomer- 

 Royal, kindly tells us that "two small faint spots in the middle 

 of a little group of faculae were photographed at the Cape 

 Observatory on December 18th last. One of the spots 

 remained to the next day, when it was smaller but darker. 

 It was photographed at Greenwich on December 19th. The 

 positions as measured were : — 



Dec. 18.— Long. 295° -3 

 .. 18.— „ 293° -5 

 ., 19.— „ 295° -1 



Lat. N. 22 -7 

 .. N. 24-2 

 .. N. 23°-.r 



This district would cross the Sun's central meridian only a 

 little after midnight on December 21-22. It almost appears 

 as if it were the starting of a new cycle of solar activity, and 

 also interesting as occurring in the northern hemisphere as 

 was foreshadowed. 



Our chart is constructed from the combined observations of 

 Messrs. John McHarg, A. A. Buss, E. E. Peacock, W. H. 

 Izzard, and the writer. 



DAY OF FEBRLARV. 



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