l82 



HARDWICKE'S SCIENCE-GOSSIP. 



affixed a small ventricle, or portal heart, which 

 impels blood in a pretty rapid current into the liver, 

 ovary and kidney, and thence through the gills, and 

 back again to the auricle, whence, having passed into 

 the ventricle, it passes into all the viscera and the 

 foot,* thence it oozes into the visceral sinuses and 

 amid a network of sinuses (open spaces) in the skin, 

 and returns to the systemic auricle by two veins. 

 There is thus a double circulation of the blood, a 

 systemic and a portal circulation ; and the beautiful 

 feathery gills subserve the sole purpose of aerating 

 the doubly deteriorated blood that has traversed the 

 kidney and the large and compact liver. The liver 

 in fact is the largest organ in the body, so that on 

 opening a sea-slug the most conspicuous object you 

 perceive is some very bilious-looking matter ; the 

 interior seems all bile, which no doubt subserves 

 essentially important purposes in the assimilating, 

 digestive, and heat-producing economy of the animal. 

 \Yith respect to the digestive system, it may be ob- 

 served that in Doris it consists of the following parts, 

 lips, buccal mass (comprising a broad or narrow 

 tongue, with sometimes a spiny prehensile collar 

 added), &c., oesophagus, salivary glands, stomach (an 

 ovate sac frequently buried in the liver), intestine 

 {which is always short), pancreas, and an enormous 

 liver. 



Such is the general size, conformation, and dispo- 

 sition of the principal life-organs oi Doris tuhcrciilata ; 

 and these, with some variations and in different 

 phases of development, prevail generally throughout 

 the genus. About lOO distinct forms or species of 

 this genus are known to exist throughout the world, 

 .and of these about twenty are recognised as British. 

 Among the latter, D. tiibei-ciilata may be regarded as 

 one of the commonest and most generally distributed. 

 During the spring and summer it is frequently to be 

 found between tide-marks, either close-closeted be- 

 neath some projecting eaves ol rock, or stranded high 

 and dry on the sands ; and sometimes when during 

 •the autumnal gales it is hurled lifeless upon the beech 

 by the wallowing seas, its cloak is observed to be ex- 

 .tensively blotched with purplish streaks and patches. 

 When in the adult condition it is about three inches 

 or more in length. Its colour is extremely variable, 

 owing no doubt to the varying condition of its liver ; 

 but when in health it is of a yellow-ochre tint. The 

 body is rather depressed, being not nearly semi- 

 globular, and tlie upper or convex surface is com- 

 pletely studded with small pimples or warts of 

 different sizes. The branchial plumes are very large, 

 eight in number united at the base, tripinnate (thrice 

 feathered) and surround a prominent tubular vent. 

 The cloak is stiffened especially around the flanks by- 

 long, rough, spindle-shaped spiculas, some of whicli 



^^ * In most molluscs some part of an excretory organ, called the 

 'organ ol Uojanus," is in close relation with the veins near the 

 heart, and serves to eliminate the nitrogenous waste from the 

 i)ody. 



are slightly bent at or near the centre, and bluntly- 

 pointed at the ends. The tongue of this species is, 

 when expanded, about half an inch square, and the 

 whole of this small area bristles with minute spines, 

 which number about 6000, and are shaped somewhat 

 like the spines of the dog-rose. This organ is bi- 

 sected into two equal parts, each of which carries 

 some forty rows of seventy-two teeth, only eighteen 

 of which rows are ever on duty for grasping the 

 sponges on which the animal generally dines. The 

 teeth when magnified are seen to be stout, uniform in 

 shape, strongly hooked, and marshalled in such a way 

 that they look like as many rows of pegs on which a 

 liliputian hat might be hung. 



[To be continued.) 



A GEOLOGICAL EXCURSION TO SWIT- 

 ZERLAND. 



By Dr. Rudolf Haeusi.er. 



\Conlinncd from page 13.] 

 r.VRT II. 



MoLASSE Quarry of the Kalofen. 



THESE beds represent the material deposited 

 along the coast of an arm of the molasse sea, 

 the ripple-marks being often very distinct. They 

 contain washed-in fossils of the Jurassic rocks which 

 formed the cliffs of the miocene sea. With the 

 exception of a few molluscs, fossils are scarce, being 

 almost entirely broken by action of the waves. 



Near Umiken thick banks of conglomerates alter- 

 nate with the molasse-beds, which in this locality 

 are full of oysters. On returning to Brugg, and 

 crossing the railway bridge, a bed of ferruginous 

 {eocene) marl containing flints with upper Jurassic 

 fossils, is worth visiting. Lower down, near the 

 town, below the Freudenstein, the vertical- cliffs 

 consist of limestones belonging to the zone of Am. 

 Achilles, with numerous bivalves {F/iol. saitata, 

 Thracia snprajiireusis, &c.). They are covered by 

 the more local Letzischichten, with Balanocriniis 

 subteres, Pholadomya cor, &c. 



From Brugg, an excursion to the famous Scham- 

 belen, in the valley of the Reuss, can be finished in a 

 few hours. Take the main road to Miilligen, passing 

 the old monastery of Kiinigsfelden (with fine stained 

 windows and the cell of Queen Agnes) and the new 

 cantonal lunatic asylum and hospital. The road on 

 the left side of the river cuts a series of triassic and 

 Jurassic rocks, amongst which the following can 

 easily be recognised by their characteristic fossils. 

 The Lettenkohle is represented by : — I. Dolomitic 

 limestones with Gervillia socialis and Myophoria 

 7ndgaris ; 2. Alum slates with Estheria miiiuta and 

 Lucina Bronni ; 3. Bone bed with Saitrichthys Mou- 

 i^eolti, S. acnniinatits, Acrodus Gaillardoli, &c. 



