GENUS OPHRYDIUM. 



m 



come in contact, often selecting as a nucleus for their new establishment the 

 minute gas-bubbles on the surface of the water, and from which were developed 

 the floating spheroidal clusters. In this green variety more usually, also, a 

 number of animalcules congregated together and assisted in the fabrication of 

 the common gelatinous matrix. In the hyaline type, on the other hand, a single 

 zooid only laid the foundation of the new colony, while the leaves of some water- 

 plant were invariably selected as the fulcrum of attachment. 



Ophrydium Eichornii, Ehr. Pl. XLI. Figs, 10-18. 



Bodies attenuate, cylindrical, subfusiform and tapering posteriorly, 

 mounted on a slender pedicle whose length equals or exceeds that of the 

 extended body, and which is continuous and undivided to its basis of 

 attachment ; the cuticular surface finely annulate transversely, very elastic, 

 and enabling the animalcule to assume a variety of positions ; parenchyma 

 perfectly transparent and colourless ; forming attached hemispherical 

 gelatinous colonies of numerous closely approximated individuals, occa- 

 sionally dividing by transverse fission. Length of expanded zooids i-ioo" 

 to 1-50". Hab. — Fresh water, on Anacharis, 



The author received a species corresponding with the above diagnosis, in some 

 quantity, growing on Anacharis, in November 187 1, and also in March 1874, 

 from Mr. Thomas Bolton, he having collected it in the neighbourhood of Stour- 

 bridge, Worcestershire. At that earlier date it was proposed to distinguish this 

 variety by the title of Oph>ydini)i longipes, no other representative of the genus 

 having so far been authentically certified to possess a pedicle which penetrated to 

 the basis of attachment of the common gelatinous mass. A similar feature has 

 nevertheless been since shown by Wrzesniowski to obtain in O. versatile, though 

 in the ordinary form of that species it presents a more complex, ramifying aspect. 



Since formulating the foregoing diagnosis, the author has obtained access to Ehren- 

 berg's brief diagnosis of his Ophrydium Eichornii* which may be thus summarized : — 



Animalcules elongate, hyaline, subfusiform, for??titig small, hemispherical, trans- 

 parent polyparies, with centrally radiating caudal seta;, attached to Ceratophyllum and 

 other water-plants. Length of bodies 1-44" to 1-72". 



This Ophrydium is further identified by Ehrenberg with a so-called species of Vorti- 

 cella, imbedded in a gelatinous matrix, described by Eichorn in the year 1838. There 

 can be little doubt that the so-called caudal setas of Ehrenberg's type correspond 

 with the characteristic pedicles of the present form, which exhibit in profile, as 

 shov^n at PI. XL. Fig. 10, a similar radiating aspect, while the size, habits, and other 

 details, so far as recorded, agree so completely with those of the author's Ophrydimn 

 longipes that the two must be regarded as identical and the earlier name of 

 O. Eichortiii be retained. The author is also inclined to accept Wrzesniowski's 

 var. hyalinum of O. versatile as synonymous with the present species, this identity 

 being self-evident upon a comparison of the diagnoses of the two forms. 



The colonies of Ophrydium Eichornii first received from Mr. Bolton contained 

 at the most about one hundred zooids, the entire hemispherical mass yielding 

 in its longest diameter a measurement of about the one-eightieth part of an 

 English inch. Still more recently, April 1881, colony-stocks of much larger 

 dimensions have been obtained through the same source, the finest of them 

 measuring no less than the one-eighth of an inch across and enclosing many 

 hundred animalcules. In some of the smallest colonies examined there were no 

 more than four enclosed zooids, each possessing a long and fully developed pedicle ; 

 this last named circumstance is of special importance as distinguishing it from the 



* ' Bericht. der Akad. zu Berlin,' p. 191, 1853. 

 VOL. II. 



