87 



og imellem disse Længdestriber sees hist og her aæsten 

 runde Cinclides; opad gaar Capitulum over i Skiven, 

 der er rund, fra 12 — l-t"'" bred, kun svagt hvælvet. I 

 Midten er den aflange Mund med 2 Gonidiegruber og 

 foldede Læber med 6 lancetformede Polder paa liver Side 

 af Mundvigene; hver Fold eller Plig har paa den aborale 

 Side en temmelig dyb Fure. Tab. XI, Fig. 12 a. I hver 

 Mundvig (Gonidiegrube) sees en liden Gonidialknude, Tab. 

 XI, Fig. 12 b. Fra Munden udstraale temmelig tætstaaende, 

 fme Linier hen til Peripherien. hvilke ligeledes antyde 

 Skillevæggenes Insertioner paa Skiven. Dennes ydre Rand 

 er jævii og forsynet med 2 Rækker 

 retraktile Tentakler, 12 i hver Række. 

 inderste Række ere meget tykkere og 

 end de i den ydre Række, Tab. IV, Fig. 10. Nedad gaar 

 Capitulum over i Scapus; denne er krumboiet, omkring rid""" 

 lang. 10 — 12""" bred foroven, men smalner hetydeligt af. saa 

 at den nederste Del, hvor den gaar over i Physa, kun er 

 5_6»"» bred. Tab. IV, Fig. 10 b; Tab. XI. Fig. 1, 2 b. 

 Den er stærkt inkrusteret med Sand, Foraminiferer, Stumper 

 a f Skjæl samt smaa, sorte, haarde Legemer og ikke retraktil, 

 men vel kontraktil; naar saa den øverste Del, Capitulum, 

 med Skive og Tentakler trækker sig ind. lukker Scapus 

 sin; ganske, saa at der kun sees en yderst lin Indsænkning 

 i Centrum. hvori man med Loupen kan opdage en haarfin 

 Aabning. Tab. XI, Fig. 2. Scapus kan forøvrigt forlænge 

 og forkorte sig efter Dyrets Forgodtbefindende. 



korte, alternerende, 



Tentaklerne i den 



kanske lidt hengere, 



Physa udvider sig halvkugleformigt, er omtrent \b mm 

 bred og ligesom Scapus overalt inkrusteret paa lignende 

 Maade som denne, Tab. IV, Fig. 10 r, 11 a. Den øverste 

 Flade er stærkt hvælvet, imedens den underste kun er 

 lidet konvex; men forresten forandres Formen, eftersom 

 den kontraheres mere eller mindre. Stundom antager den 

 næsten Kugleformen, Tab. XI. Fig. 1 c, 2 r. til andre 

 Tider bliver den temmelig flad, næsten skiveformig og ligner 

 da Fodskiven paa en Phellia, Tab. IV, Fig. 10 c. Denne 

 Del af Dyret er overmaade irritabel, saa at den mindste 

 Berørelse fremkalder ikke alene Kontraktioner i selve Physa, 

 men gjør, at Capitulum med Skive og Tentakler hurtigt 

 trækker sig ind. Det var ganske interessant at se, hvor- 

 ledes Physa skiftede Form. naar Dyret enten vikle læste 

 sig i Sandet, eller vikle forandre Sted. I første Tilfækle 

 dannede den en Konus og borede sig paa den Maade et 

 Stykke ned i Sandet, hvoretter den antog den udvidede 

 Kugle- eller Skiveform og blev da ganske skjult af det 

 overliggende Sand. Dyret stod da temmelig fast, udloldede 

 sig frodigt i Observationskarret og syntes i det Hele tåget 

 at beånde sig meget vel. Efter nogle Dages Forløb blev 

 det uroligt ; Physa forandrede atter Form, frigjorde sig fra 

 Sandet, paa hvis Overflade hele Dyret nu laa og forsøgte 

 ved Kontraktioner og ormformige Bevægelser af hele 

 Kroppen at forandre Plads. hvilket ogsaa rykkedes. Nu 



divisional walls (septai, and between these longitudinal 

 stripes, almost round cinclides are here and there seen. 

 At the toj) the capitulum passes over into the disc, which 

 is round and from 12 — 14""" in breadth, and only slightly 

 arcuate. In the middle is the oblong mouth witli 2 gon- 

 idial grooves and folded labiæ; there are 6 lanceolate folds 

 upon each side of the oral angles, and each fold or flap 

 has a rather deep furrow on its aboral side (Pl. XI. fig. 12 </). 

 In each mal angle (gonidial groove) a small gonidial nodule 

 is seen (Pl. XI, hg. 12 h). Rather closely placed, fine 

 lines radiale from the niouth to the periphery, and these 

 also indicate the insertions of the divisional walls on the 

 disc. The outer margin of the disc is even. and is fur- 

 nished with 2 series of short, alternating, retraetile ten- 

 tacles, 12 in each series. The tentacles in the innermost 

 series are somewhat thicker and, perhaps, a little longer 

 than those in the outer series (Pl. IV, fig. 10). Lower 

 down the capitulum passes over into the scapus. The 

 scapus is bent, measures about f»!)""" in length. 0) — 12""" 

 in breadth at the top. but narrows considerably lower 

 down. so that at the lowest part, where it passes over into 

 the physa. it is only 5— 6'""' in breadth (Pl. IV, fig. 10 6; 

 Pl. XI. fig. 1, 2 h). It is strongly encrusted with sand, 

 foraminifera, fragments of shells, and small, black, hard 

 bodies, and is not retraetile but. presumably, is contrac- 

 tile. When the uppermost part. capitulum with disc and 

 tentacles, retracts, the scapus completely closes itself, so 

 that only an exceedingly minute cavity is observed in the 

 centre, in which, with the assistance of the magnifier. a 

 capillary orifice may be seen (Pl. XI, fig. 2). The scapus 

 can, besides, be lengthened and shortened at the will of 

 the animal. 



The physa expands itself hemispherically, and measures 

 about 15""" in breadth, and it is, like the scapus, everywhere 

 covered with an encrustation in the same manner as tint 

 is (Pl. IV, fig. 10 c, 11 «). The uppermost surface is 

 strongly arcuate, whilst the lowest one is only a little 

 convex. but the fonn changes, however, according as it 

 more or less contracts. Sometimes it assumes almost the 

 spheriform (Pl. XI, fig. 1 c, 2 c), but at other times it 

 becomes rather flat. almost discoidal, and then resembles 

 the pedal disc of a Phellia (Pl. IV, fig. 10 c). This part 

 of the animal is particularly sensitive, so that the slightest 

 touch produces not only contractions in the physa itself, 

 but also causes the capitulum, with disc and tentacles. tu 

 be quicklv withdrawn. It was quite interesting to sec 

 how the physa changed shape when the animal was either 

 about to secure itself in the sand or to change its situa- 

 tion. In the first-named case it formed a cone. and in 

 that way bored itself a little way into the sand, after 

 which operation it assumed the expanded spheriform or 

 discoid form and was then quite hidden liv the super- 

 incumbent sand. The animal then stood pretty firmly, and 

 unfolded itself luxuriantly in the glass-jar, and appeared 

 altogether to quite enjoy itself. After the expiry of a 

 few days it became uneasy , the physa again changed its 

 form. loosened itself from the sand upon whose surface 



