566 MERISTIC VARIATION. [part i. 



form is known to occur in many kinds of Tapeworms, and especially in 

 Cysticerci. Leuckart, Parasiten d. Menschen, pp. 501 — 2, cp. p. 577. 

 [Case withfii'e suckers mentioned, ibid., p. 578.] 



In another form of abnormality the chain of segments has three 

 longitudinal flanges, formed, as it were, by the union of two chains of 

 proglottides having one edge in common. Head not found, but several 

 cases known. Genital openings in one case all upon the common edge. 

 Leuckart, ibid., p. 574. Cp. Cobbold, Trans. Path. Soc, xvn. p. 438; 

 Levacher, Comptes Yendus, 1841, xm. p. 661. 

 882 Bifurcated chains of proglottides have also been seen, e.g. specimen 



of TaBnia (cysticerci) tenuicollis, which bifurcated several times in 

 terminal portion, though normal in front of this. Momez, Bull. >Sci. du 

 No rd, x. p. 201. See also Taenia saginata ? Leuckart, I. c, p. 573. 



Brachiopoda. 

 883. Acanthothyris spinosa (Rhynchonellida^): case of duplicity 



I u 



Fig. 209. Acanthothyris spinosa, No. 883. Case of duplicity. (From P. Fischer.) 

 I. Seen from ventral valve. II. Looking between the valves. 



as shewn in Fig. 209. Fischer, P., Jour, de Conchyl. S. 3, xix. p. 

 343, PL xm. figs 4—7. 



HOLOTHURIOIDEA. 



884. Cucumaria acicula : specimen made up of two individuals 

 cohering laterally at posterior ends. Schmeltz, Verh. d. Ver. f. 

 naturw. Unterhaltung, Hamb., 1877, iv. p. XV. 



885. Cucumaria planci : case of second mouth and ring of tenta- 

 cles borne on a lateral bud-like projection. Ludwig, H., Z.f. w. 

 Z., liii. Supp. p. 21, PI. v. 



886. Ccelenterata. Forms which are commonly simple, such as Actinia or Sagartia, 

 are rarely found with two discs seemingly due to incomplete division, which in 

 these forms may take place longitudinally [?] as well as by ordinary budding. 

 Gosse, P. H., Sea-Anemones, p. xxi., &c. See also Guyon, Zoologist, p. 7026, fig. 



Similar occurrences, not distinguishable from budding, have been seen in 

 Medusas, e.g., Phialidium variabile, Davidoff, Zool. Anz., iv. p. 620, fig.; Gastro- 

 blasta raffaeli, Lang, A., Jen. Ztseiir., xix. p. 735. An interesting case of this kind 

 * was seen in Cordylophora lacustris. Several polystomatous specimens were found 

 on a particular mass of Cordylophora, but were not found on all colonies gathered 

 with this mass and had not been seen previously in specimens from the same 

 locality. [Further particulars.] Price, H., Q. J. M. S„ 1876, p. 23, figs. 



Protozoa. Double and triple monstrosity has been seen in several 

 Foraminifera, see e.g., Dawsox, Canad. Nat., 1^70, p. 177, figs.; Balkwit>l 

 and Wright, Trans. B. Irish Ac, 1885, xxviii. p. 317, PL xiv., &c. 

 [As to cases in Stentor, see Balbiani, J. de Vanat., 1891, No. 3, but these 

 are doubtless examples of regeneration and duplicity following injury.] 



