26 



NATURE 



[November 2, 191 1 



left by the spines and tf«-th on n smooth plasticine surface 

 wire txhibited with the h.lp of ihf lantern. 



Healthy urchins, movinj* under watrr ovor approximately 

 horizontal surfaces, do not, as a rule, use the lantern for 

 movement, the greater part of their weight beinj{ neutralised 

 by the water, fhsre are, however, certain conditions, both 

 normal and experimental, in which the lantern plays an 

 important part in locomotion. Dr. Gemmill brought for- 

 ward evidence in favour of the view that the locomotor 

 action of the lantern is a particular manifestation of a 

 fundamental rhythmic activity, which can also subserve 

 feeding, boring, respiration, and circulation, and possibly, 

 in addition, the maintenance of turgescence within the 

 ampullne of the water- vascular system. 



Dr. Gemmill also gave a lantern demonstration on the 

 development of the star-fish, Solaster endeca. 



Echinoderm Hybrids. 



Mr. H. M. Fuchs presented observations on the experi- 

 mental control of dominance in echinoderm hybrids, using 

 Echinus viiliaris and E. uctitus. Dr. Shearer and Mr. 

 de Morgan had found that when these two species are 

 crossed the characters of the hybrid larv£e are always the 

 same as those of the maternal parent, and this was found 

 by Mr. Fuchs to hold good also when the eggs were kept, 

 during the cleavage period, in s' ;i wai^r with increased 

 and decreased OH ions.' 



The Gonads of the Urchin Echinocardium cordatum. 



Prof. Caullery (Paris) traced the annual cycle of changes 

 in the gonads of this urchin. From July to the end of 

 the year the gonads are almost entirely composed of large 

 cells, each of which contains a vacuole and numerous 

 spherules of reserve substance. In males these cells 

 exhibit, among the reserve material, numerous spermatozoa, 

 agglutinated into pockets, which have been ingested by 

 the cells ; in females, fragments of degenerating ova are 

 seen between the cells. At the periphery of the gonad 

 there are either small masses of spermatogonia or oocytes. 

 Growth of the genital products takes place, in part owing 

 to the presence of the reserve-laden cells, at the end of 

 winter, and the period of maturity, at Wimereux, extends 

 from April to the end of May. The reserve-containing 

 cells are gradually pushed towards the centre of the acini, 

 and in some localities, e.g. Naples, disappear, but at 

 Wimereux they do not fully disappear. Up to the end of 

 May there have been formed, in the testes, for example, 

 only the sexual cells, but henceforward there are produced 

 numerous cells, each of which elaborates groups of granules 

 and contains a large vacuole. This is the new reserve 

 tissue, which soon forms a continuous peripheral layer. 

 By the end of June the sexual elements in course of forma- 

 tion exhibit signs of degeneration, e.g. fragmentation of 

 the oocytes and pycnosis of the spermatogonia, but ripe 

 sexual products are for some time longer emitted. After 

 Julv the emission ceases, and the sperms remaining in the 

 testis become agglutinated and are ingested bv the reserve 

 cells, which gradually occupv the whole gonad. In star- 

 fishes there is no reserve tissue, and the gonads, after 

 havmg almost filled the arms, hproino so much reduced as 

 to be almost imperceptible. 



Observations on Boring Molluscs. 

 Mr. W. T. Elliot^ and Miss B. Lindsav described 

 observations on Zirphaeu (Pholas) crispata and Saxicava 

 rugosa, made on the shore at St. Andrews, which confirm 

 the statement of Prof. Mcintosh that the method of boring 

 of these mol uses is mechanical, and not chemical. Both 

 molluscs work by means of a partial vacuum produced bv 

 cooperation between the mantle and foot, supplemented bv 

 scraping movements of the shell, which in Zirphaa are 

 continuous and progressive during the time of boring. 

 Reference was made to the importance of boring organisms 

 in connection with coast erosion. 



l,LJ^'^ experiments were prompted by recent work of H. D. Tennent 

 (1900, loio) who crossed H.pponoe <? X Toxopneustes 9 and T. <<xH 9 

 obta.n.nif m both cases lar%a: with a preponderance of Hipponoe characters.' 



incres^ed and decreased concentration of OH ions he claims to have altered 

 cWctere""" *" """ * decrease of OH ions gave Toxopneustes 



NO. 2192, VOL. 88] 



The Species of Balanus Collected by the " Siboga. " 

 Dr. P. P. C. Hock (Haarlem) gave an account of soir. 

 of the species of Balanus collectwi in the Malay ,r- i:- . ' 

 during the cruise of the Siboga. Of the i 



species collected, nineteen are new. Few sjj 



brought up from great depths ; most of them were tak' 

 at a not greater depth than 90 metres. Some were brou^ 

 up from 564, 289, 216, 275, 304, and 390 metres respective! 

 but the species represented in the first three cases W' 

 collected also at a depth of less than 100 metres. D 

 Hoek described some of the features, especially the labru: 

 which he had used in classification. 



The Renal Organs of Squilla. 



Dr. VV. N. F. Woodland described the renal organs — 

 maxillary glands — of Squilla. In an Erichthus larva 2 mm. 

 long the gland consists of a short narrow tube, opening ' 

 externally on the maxilla and ending internally in a slightly 

 dilated end sac. In an older larva, 12 mm. long, the 

 gland has become divided into two thin-walled compart- 

 ments — the kidney proper and the end sac — lying side by 

 side and communicating by a small aperture at their 

 posterior ends. A little later the walls of the gland become 

 invaginated, forming internal lamellar folds containing 

 extensions of the ha;mocoele, a process which continues so 

 extensively that, in the adult, the cavity of the gland is 

 almost entirely broken up into a network of spaces. Other 

 features of the internal anatomy were also referred to, 

 namely, the presence of a well-developed nauplius eye, 

 rectal glands, and a very short proctodaeum, which forms 

 a wide cloaca-like cavity. 



A Reconstructed Trilobite. 



Dr. Malcolm Laurie gave an account of the anterior end 

 of a trilobite (Calymene), which he has studied by means 

 of grinding away definite and very thin layers of the fossil, 

 photographing each exposed surface and reconstructing the 

 specimen in wax on an enlarged scale. He exhibited the 

 reconstruction, and pointed out that, although the mouth 

 has been considered as opening behind the hypostome, the 

 size and form of the latter render it improbable that the 

 mouth opened behind it. Apparently the anterior margin 

 of the hypostome projected ventrally, while the inturned 

 margin of the neighbouring carapace also projected 

 ventrall}', the two forming low-er and upper lips respectively 

 to the mouth. In a line between the lateral margin of the 

 glabella and the eyes there is a long conical structure, more 

 than two-thirds the length of the carapace, divided into 

 joints by annular thickenings. It is impossible to state 

 certainly whether this is in situ, but its structure resembles 

 that of an antenna. If it be such it must have b*?^ 

 attached to the body behind the hypostome, as otherw' 

 it could not have been withdrawn when the animal roll- . 

 itself up. This appears to be another instance of a po?t- 

 oral appendage assuming an antennary function, as in 

 Phrynus and Thelyphonus. 



British Symphyla and Diplopoda. 

 Mr. R. S. Bagnall gave a rapid survey of the Briti- 

 Symphyla, pointing out the characters of the gene 

 Scutigerella and Scolopendrella and of some of their speci' 

 A year ago only one species of the former was known fr< 

 Britain; in 1904, when Hansen's monograph of the ore! 

 appeared, eight European forms were recognised ; of thes 

 six have now been found in the north of England, and there 

 have also been discovered four other well defined and appar- 

 ently new forms. Mr. Bagnall recognises four species 

 Scutigerella and seven of Scolopendrella. He also record 

 four diplopods from the north of England, each of whi 

 represents a genus previously unknown to the Brit:- 

 fauna, and, from the same locality, a new pauropod, t: 

 first British example of the Eurypauropodidae. 



Mimicry in African Butterflies and Moths. 

 Prof. E. B. Poulton exhibited three groups of mim*^ 

 butterflies collected at Entebbe. Uganda. These group= 

 were centred round species of the distasteful family 

 Acraeinae. Among the mimics were species of Acraein.'r 

 showing that members of this family acted as mimics a:^ 

 models, a fact supporting the theory of Fritz Miiller . 



