before a vowel properly zyg-, repr. Gr. ζυγο-, combining form of ζυγόν yoke; occurring in various scientific terms, of which the more important will be found in their alphabetical places. (In terms of Biology the prefix often refers to conjugation or zygosis as a method of reproduction: see CONJUGATION 5.)
Zygocardiac a. [CARDIAC A. 4], denoting an ossicle in the stomach of the crayfish and other crustaceans (see quot., and cf. PTEROCARDIAC, UROCARDIAC). Zygodont a. (Gr. ὀδούς, ὀδοντ- tooth], having molar teeth with an even number of cusps arranged in pairs; having cusps thus arranged, as a molar tooth. Zygoneurous a. [Gr. νεῦρον nerve], applied to an arrangement of the nervous system in certain gastropod mollusks, in which the pallial nerve of each pleural ganglion unites directly with the ganglion of the visceral commissure of its own side (opp. to dialyneurous); so Zygoneury, zygoneurous condition. Zygophiuran a. and sb., belonging to, or a member of, the division Zygophiuræ of ophiuroids, having special structures that limit the movement of the ossicles of the arms (cf. zygospondyline below). Zygophyte [Gr. φυτόν plant], a plant that reproduces by conjugation. Zygopterid sb. and a. [Gr. πτερόν wing], a member of, or belonging to, the division Zygopterides or Zygoptera of dragon-flies, having all the wings nearly or quite equal in size. Zygosperm [Gr. σπέρμα seed] = ZYGOSPORE. Zygosphere [after OOSPHERE], either of the two conjugating cells or gametes which form a zygospore. Zygospondyline a. [Gr. σπόνδυλος vertebra, joint], applied to those ophiuroids in which the arms are incapable of being coiled round straight objects, the movements of their ossicles being limited by internal pits and processes. Zygostyle [STYLE 10] (see quot.). Zygozoospore, a zoospore formed by conjugation; a motile zygospore.
1877. Huxley, Anat. Inv. Anim., vi. 319. A large, elongated postero-lateral or *zygocardiac ossicle.
1888. Amer. Naturalist, XXII. 832. The *zygodont (quadritubercular) type.
1901. Proc. Zool. Soc., 466. A Vivipara possessing a single *zygoneurous connection on the left and the normal dialoneurous relationship of the nerves upon the right. Ibid. (1892), 182. For the *Zygophiurans assistance in classification will be gained from Ljungman’s well-known work.
1885. Goodale, Physiol. Bot., 439, note. The sexual process in *Zygophytes is characterized by the confluence of the protoplasmic masses of two very similar cells by which a new mass is formed as the starting-point of the new individual.
1900. W. J. Lucas, Brit. Dragonflies, 53. A *Zygopterid [wing]. Ibid., 34. Nymph of a Zygopterid Dragonfly.
1880. A. W. Bennett & Murray, in Q. Jrnl. Microsc. Sci., XX. 417. The conjugated *zygospheres … constitute a *zygosperm.
1892. Proc. Zool. Soc., 1 March, 178. To regard the strepto-spondyline type [of ophiuroids] as earlier than the *zygospondyline.
1881. Mivart, Cat, 463. The caudal vertebræ are few and end in a bone, shaped somewhat like a ploughshare, called the *zygostyle.
1881. Nature, 28 July, 292. Family Protococcaceæ. Genus Chlorochytrium.… Each cell becomes resolved into spherical zoospores, which upon leaving the mother-cell conjugate within the gelatinous envelope. The *zygozoospores before becoming surrounded with a membrane make their way … into the intercellular spaces of living plants.
