June 20, 19 18] 



NATURE 



19 



was shown further that the frequence-rale of the 

 reflex discharge has not reached its Hniit under a 

 stimulation of 75 per sec, but surpasses that degree, 

 though by what amount the method cannot sa)'. The 

 maximal mechanical power of a muscle contracting 

 under spinal reflex action is frequentl}' as great as 

 the maximal which can be evoked from it by direct 

 faradisation of the motor nerve itself. 



. Geological Society, June 5.--Mr. G. \V. Lamplugh, 

 president, in the chair. — W. D. Lang : The Keles- 

 tominae, a sub-family of Cretaceous cribrimorph 

 Polyzoa. The Kelestominae are a sub-family of Pelma- 

 toporidae. The latter are a family of Cretaceous 

 cribrimorph Polyzoa, the costae of which are prolonged 

 upwards as hollow spines from the median area of 

 fusion of the intraterminal front wall. The broken 

 ends of these spines form a row of pelmata (or, if 

 small, pelmatidia) on the intraterminal front wall. The 

 Kelestominae are Pelmatoporidae with an apertural 

 bar, each half of which is bifid ; and the proximal and 

 distal forks, of each half are fused with the corre- 

 sponding forks of the other half. The fused distal 

 forks are also fused with the proximal pair of aper- 

 tural spines, which are greatly enlarged. The simplest 

 known form of this arrangement is seen in the genus 

 Kelestoma, Marsson. Morphasmopora, unlike Kele- 

 stoma, retairts a small number of costae and a short 

 cecium ; but the thickness of the proximal apertural 

 spines, which are scarcely recognisable as such, 'is 

 enormously increased ; the thickness of the bifid aper- 

 tural bar is also increased. — Dr. R. L. Sherlock : The 

 geology and genesis of tin Trt friw pyrites deposit. 

 This pyrites deposit is worked at Cae Coch Mine, 

 on the western side of the Conway Valley (North 

 Wajes), about one mile north of Trefriw. A band of 

 pyrites, about 6 ft. thick, and of considerable purity, 

 rests on the inclined top of a thick mass of diabase, 

 which is shown to be intruded into the Bala shales 

 that cover the ore-body. Pyrites deposits are classified 

 by Beyschlag, Vogt, and Krusch into four groups :— 

 (i) Magmatic segregations; (2) formed by contact- 

 metamorphism ; (3) lodes; (4) of sedimentary origin. 

 None of these modes of origin, however, will account 

 for the Trefriw pyrites. The conclusion arrived at is 

 that the diabase was intruded below a bed of pisolitic 

 iron-ore. 'Hot water containing sulphuretted hydrogen, 

 given off from the intrusion combined readily with the 

 pisolites, which were in the form either of oxide 

 or of silicate of iron, and formed pyrites. The grap- 

 toiitic horizon at which the pisolitic ore occurs usually 

 contains some pyrites, and this would be added to 

 I hat derived from the above reaction. 



I.innean Society, June 6.— Sir Da\id Prain, presi- 

 dent, in the chair.- -C. C. Lacaita : A revision of some 

 critical species of Echium as exemplified in the 

 Linnean and other herbaria, with a description of 

 Kch'ium ju.laeuni, a new species from Palestine. — 

 Capt. A. \V. Hill : A series of seedlings of Cyclamen. 

 Normally .only one cotyledon develops, the other re- 

 maining as a rudiment at the apex of the hypocotyl 

 or tuber. If the lamina of the cotyledon be removed, 

 new laminae arise as outgrowths from the petiole 

 just below the cut surface; but if the C9tyledon with 

 its petiole be removed, the rudiment of the second 

 cotyledon is stimulated to develop into an assimilatini' 

 organ. On removal of the lamina of this second 

 cotyledon new laminae will be formed from the inner 

 edges of its petiole . close to the apex, exactlv as is 

 '^he case with the cotyledon proper. When plumular 



ives are so treated no new laminae are regenerated. 



iither cotyledon leaf-cuttings will produce roou 

 in the base of the petiole, while plumular IimI- 



\'<"). 2538, VOL. lOl] 



cuttings remain rootless. — R. Paulson and S. Hastings : 

 The relationship between the symbionts in a lichen. 

 Ciadonia digitaUi, Hoffm., is the lichen used as 

 material for many of the authors' preparations. This 

 plant grows at the base of trees in shady woods in 

 Hertfordshire and Essex, as well as in most northern 

 localities. The gonidium is spherical, except when 

 subject to pressure from other gonidia. The dianuter 

 of fully developed cells ranges from 8 to 15 /x ; tli. 

 chloroplast in the mature gonidium has an un.Ncn 

 surface; after fixing and staining, minute reticulation 

 of the cytoplasm is evident; the so-called pyrenoid is 

 large and central, and exhibits a distinct structure 

 throughout the substance, its diameter is roughly one- 

 third that of the chromatophore ; a small lateral body 

 stains darker than the pyrenoid, it is very conspicuous 

 in many of the preparations surrounded by a very 

 lightly stained area. Twin gonidia frequently occur; 

 there is no vegetative cell-division of the gonidium ; 

 the increase in the number of gonidia results from the 

 formation of autospores, reduced zoogonidia ; there is 

 no penetration of f^onidia by hyphae. 



Mathematical Society, June 13.— Prof. E. W. Hobson, 

 vice-president, in the chair.- Prof. M. J. M. HiU : An 

 assumption in the theory of singular solutions of 

 ordinary differential equations of the first order.— 

 Col. A. J. Cunningham and Th. Cosset : Ouartic and 

 cubic residuacitv tal.lcs. (\.l. A. J. Cunningham: 

 Lucas's process applied lu composite Mersenne 

 numbers.— Dr. A. E. Western : The Gaussian period 

 numbers and the conditions that 2 should be a residue 

 of a i6th or 32nd power.— T. W. Chaundy : The aberra- 

 tions of a symmetrical optical system.— T, L. Ince : 

 The rotation groups of the regular figures in four or 

 more dimensions.— J. H. Grace: (i) An analogue in 

 space of a case of Poncelet's porism. (2) Note on 

 enumerative geometry.— E. K. Wakeford : Posthumous 

 MS. discovered in his kit. 



Edinuirgh. 

 Royal Society, June 8.— Dr. John Home, president, 

 in the chair.— Miss L. H. Huie : The formation of tJie 

 germ-band in the egg of the holly tortnx moth 

 (Eudemis naevana). The following mam results were 

 obtained. The egg laid in July and August is much 

 flattened, having the form of an oval scale, the ventral 

 surface of which adheres to the leaf. The shape of 

 the egg and the transparency of the envelopes make 

 this a convenient material for the study of the early 

 development of a lepidopterous insect. An account 

 was given of the stages leading to the formation ot 

 the blastoderm, the ventral plate, vhe amnion, the 

 germ-band, and the " inner layer." This last becomes 

 segmented almost at once, but the ectoderm remains 

 unsegmented during the winter.-Prof. R. A. Sampson : 

 Studies in clocks and timekeeping. No. 2. : The cir- 

 cular equation. The present communication is the 

 second of a series of studies executed at the Royal 

 Observatory upon precision clocks and timekeeping. 

 The astronomical interest of these studies comes from 

 their ultimate bearing on the rotation of the earth. 

 which is our standard of timekeeping;. 1 h. n- plan 1- 

 to accumulate with sufficient care and d<iail t!ie n<ee>- 

 sary observations and discussion- upon all point- at 

 pie'sent obscure or imperfectU treated wliuh nia\ 

 >ek. 1 hi i^resent paper 

 ■ llicoittieal effect upon 

 on of air of oscillation 

 il;e, wiiieh aiv l<no\\n. 

 „■ eonvenieiit i.fr-vnee. 

 ■lira! r.'>uli< w itli a. tual 

 futui-- in.-niliei- of ill.' 

 s,)Uiul-\va\es and other 



