November 2, 



1911] 



NATURE 



25 



apparatus could never have been developed. Dr. Wood- 

 land believes, with Balfour, that the branchial skeleton of 

 cyclostonies is not homologous with that of gnathostomes, 

 since, for one reason, in the former the skeleton is 

 developed external to the ventral aorta and the gill vessels, 

 while in the latter it is internal. He concluded that, con- 

 sidering the visceral arches as a whole, it is incredible, if 

 the cyclostomes have originated from a gnathostome stock, 

 that the first two visceral arches should exhibit the differ- 

 ences in development (in time and form) and relationships 

 to nerves and muscles shown by the sub-ocular arch, 

 piston, and styloid cartilages, &c., when compared with the 

 jaw and hyoid arches of gnathostomes. 



Prof. Dandy, while agreeing generally with Dr, Wood- 

 land's position, pointed out that the lampreys and hags 

 differ markedly from each other. The brain of Petromyzon 

 is primitive, and in Geotria there are two pineal eyes — a 

 very primitive character ; the brain of Myxine is highly 

 modified, and pineal organs are wanting. These and other 

 facts suggest that the two subdivisions of the cyclostomes 

 have either had a separate origin or have diverged early 

 from one another. 



Mr. E. S. Goodrich held that the absence of jaws in 

 cyclostomes was not proved ; the piston apparatus is sup- 

 plied by the fifth nerve, and this region would therefore 

 seem to be homologous with the mandibular region of the 

 gnathostomes. The gill arches of larval lampreys resemble 

 those of gnathostomes, and though the relations of the 

 branchial basket of lampreys and the gill arches of 

 gnathostomes are not identical ventrally, their relations 

 dorsally are very similar, and therefore the homology of 

 tlipse structures is not disproved. Mr. Goodrich suggested 

 that the piston cartilage of Petromyzon might be homo- 

 logous with the median cartilages of the branchial 

 apparatus of gnathostomes. He demurred to the sugges- 

 tion that lampreys and hags have been independently 

 derived from the primitive vertebrate stem, for the two 

 series present certain common characters, e.g. the struc- 

 ture of the gills and heart, asymmetry of the vascular 

 system, horny teeth and piston apparatus, hypophysial sac 

 in relation to the nasal organ, which it is unlikely can 

 have been developed independently. He regarded the cyclo- 

 stomes as monophyletic, and as having diverged very early 

 into two branches, the lampreys and the hags. 



Communications on Protozoa. 



Prof. Herdman contributed a note on the occurrence of 

 the peridinian Amphidinium operctilatiim. at Port Erin. 

 This flagellate organism had not been previously recognised 

 in British waters, and was known only from the coasts of 

 Norway and Belgium. It was first observed at Port Erin 

 early last year, forming brown patches in the troughs of 

 tlie ripple marks on the beach about half-tide level. The 

 patches varied in size, but were observed for about three 

 weeks. Examination of the sea water in the neighbour- 

 hood of the patches showed that the organism was not 

 living in the water ; it lived only in the w-et sand. The 

 brown patches consisted of an almost pure culture of 

 Ainphiflinium, the only admixture being a very few 

 examples of a diatom (Navicula). Later in the year brown 

 patches of similar appearance were again observed on the 

 sand, but on examination they were found to consist 

 entirely of Navicula. The Amphidinium had disappeared, 

 but the Navicula had multiplied abundantly. Prof. Herd- 

 man cited this as a striking instance of the change in the 

 ortjanisms inhabiting the beach, a change which might 

 readily be, and no doubt had long been, overlooked. 



Major C. F. Bishop described his recent examinations 

 of sheep suffering from louping ill, and of ticks which had 

 f^ 1 on the sheep. On a film made of blood squeezed 

 f:<jm a tick, taken from a sheep which was said to be a 

 typical case of louping ill, he found a single " trypano- 

 some," about 22 /x long, in which the trophonucleus was 

 nearly central and anterior to it the large kir.etonucleus. 

 Trypanosomes have not yet been found in any of the sheep 

 examined, but Major Bishop considered it probable that the 

 organism described was connected with the disease in the 

 sheep. He also described other forms which he considered 

 to be blood parasites, and regarded as flagellates, in films 

 of blood from sheep. 



NO. 2192, VOL. 8S] 



A New Hydroid, Epizoic on a New Parasitic Copepod. 



Prof. H. F. Jungersen (Copenhagen) described a new 

 hydroid, Ichthyocodium sarcotretis, which covers more or 

 less of the exterior of the parasitic copepod Sarcotretes 

 scopeli, n.sp., which is deeply sunk into the body of the 

 fish Scopelus glacialis. The hydroid consists of polyps, 

 without tentacles, arising from a network of delicate tubes. 

 From the base of the polyps arise medusa-buds which 

 develop into free medusze (Anthomedusae). This new 

 hydroid is a corynid, related to Hydrichthys mints, Fewkes, 

 epizoic on the fish Seriola zonata. Prof. Jungersen gave a 

 full description of the characters and life-history of the 

 copepod, which belongs to the family Lernaeidas. There is 

 first a " Cyclops stage," capable of moving about on the 

 host and attaching itself by means of its strong cheliform 

 antennas ; the pupa stage is passively fixed to the host by 

 means of a hardened secretion from the rostrum. Within 

 the last pupal phase the copulatory form was observed. 

 The latter probably is for a time free-living ; after 

 impregnation the female assumes parasitic life anew, but 

 in a more intense form ; it pierces the skin of a Scopelus, 

 and, gradually growing, it penetrates the muscles, and 

 finally reaches the intestine. This copepod is found on 

 examples of Scopelus from the eastern part of the Atlantic, 

 and the triple association — hydroid, copepod, fish — seems to 

 be a regular one. The loss of tentacles of the hydroid 

 polyps seems to indicate that the hydroid in some way or 

 other depends on the fish for obtaining its food. 



Variation in the Medusa Moerisia lyonsi. 



j Mr. C. L. Boulenger gave an account of variations in 

 this Egyptian lacustrine medusa. About 15 per cent, of 

 the individuals examined were abnormal. The abnormal 

 examples fall into two groups : (i) those which deviate 

 from the normal four-rayed symmetry, and (2) those with 

 the normal number of radial canals and primary tentacles, 

 but possessing, in addition, secondary tentacles which are 

 not connected with the stomach by means of radial canals. 

 Some, of these multitentacular forms are asymmetrical, and 

 it seems that each quadrant is capable of forming secondary 

 tentacles quite independently of the other quadrants. 



xhe Crop of the Leech. 

 Prof. Marcus Hartog directed attention to the structure 

 of the septa in the crop of the leech. The crop is divided 

 into chambers separated by distinct simple septa pass- 

 ing inwards from the obvious external constrictions and 

 perforated by a central aperture, circular under ordinary 

 conditions, but vertically elongated in distension. The 

 septum is puckered at the free edge, and contains a circular 

 sphincter, but no divaricator fibres. This structure has 

 probably been so long overlooked because it is inconspicuous 

 in ordinary dissections, and is not easily recognisable in 

 the usual thin transverse sections ; it is well seen on 

 examining successive thick slices of a hardened, distended 

 leech. 



The Lantern of Aristotle as an Organ of Locomotion. 



Dr. J. F. Gemmill gave an account of his observations 

 on the locomotor function of the lantern of Aristotle in the 

 sea-urchins Echinus esculentus and E. miliaris. The 

 animal progresses, when out of the water, by a series of 

 steps or lurches, more or less well defined, in each of which 

 the urchin is raised on the tips of the teeth as on a 

 powerful central stilt. The steps have a length varying 

 from half an inch downwards, and are repeated at intervals 

 of fifty seconds or less, according to the size of the urchin. 

 There is a rhythmic backward and forward swing of the 

 lantern in the direction of progression. The backward 

 swing is accompanied by powerful protrusion of the tightly 

 closed teeth against the supporting surface, which causes 

 pushing or poling forward of the urchin. The mo%'ement 

 is aided by pushing on the part of the spines, and, after a 

 certain stage, by the action of gravity. The forward swing 

 of the lanteiyn is marked by retraction, with opening of 

 the teeth, and serves to bring the latter into position for 

 initiating a new lurch. Experiments on loading, recordina 

 surfaces, inversion, equatorial section, rotation, removal of 

 spines, &c., were also briefly noted, and examples of trnck> 



