OF THE FLOSCULARl^A. 



671 



Lacinularia sociaUs {Vmiicella so- 

 ckilis et Jlosculosa, M.) (xxxvii. 19).— 

 Envelope gelatinous, transparent, in 

 which are implanted numerous indivi- 

 dual animals, that have imitedly thrown 

 out the gelatinous secretion in which 

 they are imbedded. Body elongated, co- 

 nical pedimcle (xxxvii. 19 k) trimcated 

 and foniiing at its posterior extremity 

 a sucker, attaching the animal to the 

 foreign object supporting the entire 

 group. Trochal disc at the anterior ex- 

 tremity of the body, into which it is 

 drawn when at rest (xxxvii. 19 a), but 

 expanding into a horseshoe-shape, vnXh. 

 a double row of cilia round its margin. 

 Mouth in the notch of the ti'ochal disk. 

 Pharynx leading to a phar^-ngeal bulb 

 (19 b), in which the jaws are planted. 

 These are not stirrup-shaped, as described 

 by Ehrenberg, but composed of four 

 pieces (xxxvii. 20). (Esophagus passing 

 through the bulb reaches the first sto- 

 mach (19 c), into which two cellular 

 appendages, regarded by Ehrenberg as 

 pancreatic, open. Below this is a second 

 dilation (19 c?), furnished with several 

 short cellular caeca, and still lower a 

 third, more globular segment (19 e), 

 also fui-nished with external cellular 

 caeca, and clothed internally with long 

 cilia. From this a short intestine, ac- 

 cording to Huxley, turns upwards and 

 outwards, terminating in a cleft of the 

 integimient on the same side as the 

 mouth. This " intestine " is probably 

 the cloaca of other writers. Two water- 

 vascular canals (19 1) arise, one on each 

 side of the intestine (cloaca), and ascend 

 on opposite sides of the body towards 

 the head. They divide opposite the pha- 

 ryngeal bulb, each into three branches, 

 one of these uniting with its fellow, the 

 others teraiinating as caeca ; within these 

 are distributed five pairs of long vibratile 

 cilia. Vacuolar thickenings of the in- 

 tegument exist in several parts of the 

 body. A small ciliated sac is located 

 below the mouth, and still lower is a 

 small organ believed by Prof, Huxley to 

 be the cerebral ganglion. Two eye-spots 

 occur on the trochal disc of the young 

 animal (xxxvn. 11), but they disappea^r 

 in the adult. No male reproductive 

 organ hitherto discovered. Prof. Hux- 

 ley's description of the female organs, 

 and the development of the ova, is as 

 follows : — " The ovarj- consists of a pale, 

 slightly granular mass, of a ti-ansversely 

 elongated form (19 A), and somewhat 

 bent round the intestine ; it is enclosed 

 in a delicate transparent membrane, 



which is hardly \4sible in the unaltered 

 state, but becomes very ob^dous by the 

 action of acetic acid, which contracts 

 the substance of the ovary and throws 

 the membrane into sharp folds." 



Pale clear spaces (xxx^t:i. 7), which 

 sometimes seem to be limited by a distinct 

 membrane, are scattered through the 

 substance of the ovaiy; and in each of 

 these a pale circular nucleus is contained. 

 The nucleus is more or less opaque, but 

 usually contains from one to three clear 

 spots. These are the germinal vesicles 

 and spots of the future ova. Acetic acid, 

 in contracting the pale substance, groups 

 it round these vesicles, wdthout, how- 

 ever, breaking it up into separate masses. 

 It renders the nuclei more evident. 



The ova are developed thus : — One of 

 the vesicles increases in size ; and reddish 

 elementary granules appear in the ho- 

 mogeneous substance aroimd it. This 

 accumulation increases imtil the ovum 

 stands out from the surface of the ovary, 

 but invested by its membrane, which, as 

 the o\'um becomes separated, takes the 

 place of a vitelline membrane. 



In the meanwhile the geraiinal ve- 

 sicle has increased in size ; and its nu- 

 cleus is no longer visible. In the o^imi 

 it appears as a clear space ; isolated by 

 crushing the ovum, it is a transparent, 

 colourless vesicle. The perfect ova are 

 oval, about 1-10" in diameter, and are 

 extruded by the parent into the gela- 

 tinous connecting substance, where they 

 undergo their development. 



The changes that take place after ex- 

 trusion, or even to some extent within 

 the parent, are — 1, the disappearance of 

 the germinal vesicle (as Huxley judged 

 from one or two ova in which he could find 

 none) ; 2, the total division of the yelk (as 

 described by Kolliker in Megalotrochci), 

 imtil the embryo is a mere mass of cells 

 (xxx\Ta. 5, 6, 8, 9), from which the va- 

 rious organs of the fcetus are developed. 



The yoimgest foetuses are about 1-70" 

 in length. The head abruptly trun- 

 cated (xxxvii. 10), and separated by a 

 constriction from the body. A sudden 

 naiTowing separates the other extremity 

 of the body from the pedimcle, which is 

 exceedingly short, and provided with a 

 ciliated cavity (a sort of sucker) at its 

 extremity. The head is nearly circidar, 

 seen from above, and presents a central 

 protuberance, in -which the eye-spots are 

 situated. The margins of this protu- 

 berance are provided with long cilia, 

 which will become the upper circlet of 

 cilia in the adult. In young Laehndarice 



