December 19, 1912] 



NATURE 



449 



segments, which, unlike the buds, contains a pro- 

 longation of the alimentary canal of the stock, and, 

 like the buds, develops generative products. In the 

 earliest stage of proliferation observed, the body-cavity 

 near the region of proliferation was filled with leuco- 

 cytes, which also migrated into the cushion of meso- 

 blast present immediately within the thickened ecto- 

 derm. Mr. Potts suggested that these leucocytes 

 served a nutritive function, and also that they gave 

 rise to the greater number of the mesoblast cells, 

 from which are formed the gonads, ccelomic epithe- 

 lium, and connective-tissue. The muscular and 

 nervous systems of the bud grow out from those of 

 the stock. 



Dr. Cresswell Shearer traced the development of 

 the mesoderm and the head kidneys of Pomatoceros, 

 which he found to follow the same course as in Eupo- 

 matus (see Q.J. M.S., vol. Ivi., 191 1, pp. 56S-585). 



Papers on Echinodcnns. 



Dr. J. F. Gemmill described the development of the 

 starfish Asterias ruhens. The eggs were artificially 

 fertilised in April at the Millport Marine Biological 

 Station, and, at an early stage of segmentation, were 

 taken to the University of Glasgow, and kept there 

 in small aquaria provided with a simple "convection 

 current" system of internal circulation. Meta- 

 morphosis took place in seven or eight weeks. The 

 chief features of the bipinnaria and brachiolaria larv» 

 were described, as w'ere also several interesting cases 

 of double hydrocoel. Dr. Gemmill concluded that the 

 epigastric and hypogastric coeloms correspond on the 

 whole with one another and with the right and left 

 body-coeloms of Balanoglossus, while the dorsal sac, 

 which pulsates subrhythmically, is the homologue of 

 the "pericardial vesicle." 



Prof. E. W. MacBride gave an account of his 

 studies, made at Millport, on the development of 

 Echinocardium cordatum, the larvae of which he was 

 able, by feeding on the diatom Nitschia, to rear until 

 they metamorphosed into young heart-urchins, which 

 took place about eighteen to twenty-three days after 

 fertilisation. The egg segments rapidly and forms 

 an ellipsoidal blastula, which escapes from the egg- 

 membrane. This becomes converted into a gastrula, 

 which bears anteriorly a tuft of specially long cilia. 

 Soon the formation of the skeleton and the arms of 

 the larv-a is initiated. The ccelom arises as an un- 

 paired vesicle nipped off from the apex of the arch- 

 enteron, and becomes divided into right and left 

 halves. Both right and left ccelomic vesicles send out 

 prolongations which become pore-canals, and open to 

 the exterior, but subsequently the two pores merge 

 in a single median pore from which right and left 

 pore-canals diverge. Prof. MacBride traced the 

 metamorphosis of the larva, and pointed out ,that the 

 mouth of the young Spatangoid is surrounded by five 

 plates, from each of which springs an inw'ardly 

 directed spine, the rhythmical movements of which 

 suggest that they represent the teeth of the regular 

 Echinoids. 



Mr. H. M. Fuchs described work done at Plymouth 

 on the hybridisation of species of Echinus. Three 

 .species — E. aciittts, esculentus, and miliaris — were used 

 in the e.xperiments, and the early and variable larval 

 characters were discarded in favour of more definite 

 features developed by the later plutei. The late 

 plutus of_ E. miliaris has no posterior epaulettes, but 

 has a pair of green pigment mas-ses on the anterior 

 epaulettes; the late plutei of E. acutus and E. escit- 

 lentiis possess a pair of posterior epaulettes, but lack 

 the green pigment. In iqoo, iQio, and 191 1 it was 

 found that the inheritance of these characters in 

 reciprocal hybrids betw^een E. miliaris: and E. esctt- 

 NO. 2251, VOL. 90] 



lentus or E. acutus was invariably maternal. During 

 the spring and summer of this year the experiments 

 have been repeated, and it has been found that the 

 inheritance is different from that of previous years. 

 .•\11 cultures of the crosses E. esculentus 'i xE. 

 miliaris d and E. acutus 9 x E. miliaris 6 have been 

 maternal, as previously, with one exception. In that 

 case some of the larvas possessed posterior epaulettes, 

 some lacked them, and some had an epaulette on one 

 side only. The crosses in which E. miliaris was the 

 female parent were this year obtained only with diffi- 

 culty, and, with one exception, they showed a purely 

 paternal inheritance, i.e. an exact reversal from the 

 condition of former years. The exception mentioned 

 was the only case in which a large percentage of 

 the eggs developed ; the resulting larvae were some of 

 the paternal and others of the maternal type. No 

 parallel seems to be known for this reversal of in- 

 heritance, the cause of which is unknown, but Mr. 

 Fuchs suggested that it was due to a condition of the 

 parents and not to the environment of the larvae. 



Miss Jordan Lloyd described methods of raising 

 parthenogenetic larvae of Echinus esculentus. The 

 method found most successful consisted in treating 

 the unfertilised eggs first with butyric acid to cause 

 membrane-formation (Loeb's method), and then with 

 tannic acid and ammonia in a mixture of sea water 

 and cane sugar (Delage's method). In this way as 

 many as 90 per cent, of the eggs have produced 

 blastulcE, and the larvae were vigorous and grew for 

 the first three weeks as rapidly as larvae from fer- 

 tilised eggs. A few of the larvae completed their 

 metamorphosis, but the young urchins have not been 

 kept alive more than a few days. 



A New Parasitic Copepod. 

 Prof. H. F. E. Jungersen described Chordeurria 

 obesum, a new parasite copepod found enclosed in a 

 membranous capsule formed by the host — Astronyx 

 loveni. Sometimes these cysts are extremely nume- 

 rous, and in these cases the gonads of the host seem 

 not to develop. A cyst which encloses a ripe female 

 contains also its eggs and brood, and usually also a 

 male and empty spermatophores. Embryonic develop- 

 ment and most of the post-embryonic metamorphoses 

 occur inside the cyst. Cyclopiform larvae are liberated 

 from the cyst, and either settle in the same host, thus 

 augmenting the stock of parasites, or leave by 

 way of the bursal apertures to infect other .Astronyx, 

 which they enter through the corresponding openings. 

 In both cases the larva fixes itself by its hooked 

 maxillae, and causes the production of a cyst. The 

 larval cuticle is cast off and the adult form assumed. 

 The adult female is about 5 mm. long and sausage- 

 shaped. Eyes, mandibles, and maxillulae are wanting. 

 The mouth leads through the pharynx and narrow 

 oesophagus into a capacious stomach, but there is no 

 intestine and no anus. The adult male is not more 

 than 2 mm. long, subcylindrical in form, and has 

 fundamentally the same structure as the female. The 

 nauplius larva has the tyoical three pairs of append- 

 ages, but eyes are wanting, as in all later stages. 

 There are three metanauplius phases followed by the 

 Cyclops stage, which is liberated from the maternal 

 cyst. Prof. Jungersen stated that he could not at 

 present indicate the systematic position of this new 

 parasite. 



The Luminous Cells of Pyrosoma and Cyclosalpa. 

 Prof. Ch. Julin detailed the histological characters 

 of the luminous cells of Pyrosoma giganteuni. Each 

 of these cells contains a closely convoluted tube, the 

 wall of which is achromophile and is traversed by an 

 achromophile reticulum, on the knots of which are 



