TUNICATA. 



1189 



Family BOTRYLLIDJE, MacLeay. Syno- 

 nyms : Alcyonia, Auct. prior. ; Tethyes com- 

 posees, Savigny ; k& Reunis ou Botryllaires, 

 Lamarck ; Ics Agreges, Cuvier ; Ascidiacea, 

 pars, Blainville; Ascidies composees, Milne- 

 Edwards; Polyascidicns, Van Beneden. 



Body compound, fixed ; animals associated; 

 the tests fused together, forming* a common 

 mass in which the animals are imbedded in 

 one or more groups or " systems ; " the indi- 

 viduals not connected by any internal union ; 

 oviparous and gemmiparous. 



" If, when walking on the sea-shore, about 

 low-water mark," says the distinguished na- 

 turalist previously quoted, " we turn over 

 large stones, or look under projecting eaves 

 of rock, we are almost sure to see translucent 

 jelly-like masses of various hues of orange, 

 purple, yellow, blue, grey, and green, some- 

 times nearly uniform in tint, sometimes beau- 

 tifully variegated, and very frequently pen- 

 cilled as if with stars of gorgeous device ; 

 now encrusting the surface of the rock, now 

 descending from it in icicle-like projections. 

 These are compound Ascidians. A tangle 

 or broad-leaved fucus, torn from its rocky 

 bed, or gathered on the sand, where the waves 

 have cast it after storms, will show us similar 



Polyclinina - 



bodies, mostly those star-figured, investing its 

 stalks, winding among the intricacies of its 

 roots, or clothing with a glairy coat the ex- 

 panse of its foliated extremities. ... In 

 examining these bodies, we find that it is not 

 a single animal which lies before us, but a 

 commonwealth of beings, bound together by 

 common and vital ties. Each star is a family, 

 each group of stars a community. Individuals 

 are linked together in systems, systems com- 

 bined into masses. . . . Indeed, few bo- 

 dies among the forms of animal life exhibit 

 such exquisite and kaleidoscopic figures as 

 those which we see displayed in the combina- 

 tions of the compound Ascidians." 



Previous to the researches of Savigny, the 

 Botryllidce were regarded as Alcyonia ; Gaert- 

 ner (1774) and Renieri (1793) being the only 

 naturalists who had suspected their compound 

 nature and true affinities.* " The Memoir of 

 Savigny, published in 1816, however, threw 

 entirely new and unanticipated light on their 

 nature. He showed that they were essentially 

 Ascidians, differing from the simple forms only 

 in being united into more or less complicated 

 systems." f 



In the arrangement of Professor Milne- 

 Edwards the family is subdivided as follows : 



BOTRYLLIDJE, 



vel 



COMPOSITE 



Didemnina 



^Botryllina 



f Bistellata 

 [Unistellata - 



f Bistellata 

 I- Unistellata - 



The tribe Polyclinina (Ics Polycliniens, 

 Milne-Edwards) is characterised principally 

 by the division of the body into three distinct 

 portions, viz. a thorax, a superior abdomen, 

 and a post-abdomen. It has, however, other 

 anatomical peculiarities, such as the great de- 

 velopment of the organs of generation, and the 

 position of the heart at the inferior extremity 

 of the body. This group comprehends nu- 

 merous species, and is divisible into two 

 natural sections, recognised by the external 

 conformation of the anal orifice. In one di- 

 vision (P. bistellata) this orifice is surrounded 

 with a regular circlet of rays or marginal 

 lobules, and is exactly similar to the branchial 

 orifice. In the other division (P. unistellata) 

 the anal differs from the branchial orifice in 

 not being rayed, or at least in having merely 

 irregular marginal lobules. 



Genus SigiUina, Savigny. Common body 

 solid, elongated, erect cone ; gelatinous, 

 idunculated, isolated or attached to similar 

 mes, consisting of a single system of many 



but Professor Wiegmann subsequently (Jahresbe- 

 -icht in Archiv. 1835) gave it the appellation of 

 ^erophora Listeri, 



- Sigillina. 

 Polyclinum. 

 Aplidium. 

 Sidnyum. 

 Synoicum. 

 Amaroucium.f 

 Distomus 

 Diazona. 

 Didemnum. 

 Eucaelium. 

 Leptoclinum. 

 ~ Botryllus. 

 Botrylloides. 



individuals disposed one above another in 

 irregular circles ; branchial and anal orifices 

 each with six rays ; abdomen larger than 

 thorax ; post -abdomen long and slender 

 (fig. 769.). 



Genus Polyclinum, Savigny. Common body 

 gelatinous or cartilaginous, polymorphous, 

 sessile or slightly pedunculate ; systems nu- 

 merous, convex, somewhat stellate, with cen- 

 tral cloacal cavities ; individuals (10 to 150) 

 placed at very unequal distances from their 

 common centre ; the cavity in the common 

 tegument occupied by each animal is divided 

 into three chambers one above another by 

 contractions of its calibre ; abdomen much 

 smaller than the thorax j post-abdomen pe- 

 dunculate. 



Genus Aplidium, Savigny ; synonym, Al- 

 cyonium, Auct. Common body gelatinous 

 or cartilaginous, sessile } systems very nume- 



* For the early history of this genus, consult the 

 Memoir on Botryllus stellatus by AIM. Desmarest 

 and Lesueur, Journal de Physique, torn. Ixxx. 1815. 



f In the latest ("commemorative") edition of 

 Cuvier's Regne Animal, M. Milne-Edwards has 

 established a new subgenus, Parascidia, which has 

 eight marginal teeth on the buccal orifice. 

 4 G 3 



