396 ORDER FLAGELLATA-EUSTOMATA. 



shapes are from time to time assumed, the parenchyma and cuticle being remark- 

 ably soft and plastic, and the animalcules, as observed by the author, being exceed- 

 ingly restless, continually elongating or shortening their outline, and twisting to and 

 fro upon their pedicles. As previously intimated, it was in connection with this 

 species that the possession of flagellate appendages by the sedentary zooids was 

 determined. On several occasions these sedentary individuals were seen to detach 

 themselves from the branching pedicle and swim freely in the water after the manner 

 of EngkncB, while in other instances they were observed to absorb their flagella and 

 form ovate encystments whose enclosed contents broke up into innumerable spore- 

 like bodies. The rupture of these encystments and the liberation of their contents 

 as simple non-flagellate germs were likewise witnessed. The author is inclined to 

 believe that the Colacium stentorinnm of Ehrenberg embraces two distinct forms, one 

 with short, acuminate branches and attenuate, fusiform, biflagellate, sedentary zooids 

 of a dull green hue, corresponding with the Chloraugium stenfori/nim of Stein, and 

 another with bluntly ovate, bright green, uniflagellate animalcules forming variously 

 shaped bush-like growths, that corresponds probably with the present species. The 

 examples of Colacium Steinii, as here figured and described, were found on a species 

 of Cyclops taken from a pond near Acton in December 1877. 



Supplementary Species. 



An animalcule most nearly resembling Colacium calvum in external shape, but of 

 much more minute size — the length of the sedentary zooids not exceeding the 

 I -1 300", and that of the extended natatory ones the i-iooo" — has been recently 

 obtained by the author attached to the carapaces and limbs of a species of Cyclops 

 inhabiting pond-water from brickfields near Shepherd's Bush, London. In no case, 

 however, out of the numbers so far examined, was more than a single animalcule 

 found attached to one pedicle. The contour of these sedentary examples, while 

 quadrate, was, moreover, much more irregular, the distal or free margin being much 

 broader than the proximal one or that which is united to the pedicle. More usually 

 from two to four scarlet eye-like pigment-spots were developed in place of the single 

 one characteristic of the species previously described, while the chlorophyll-cor- 

 puscles were of much larger proportionate size, and leaving comparatively small 

 interspaces in the exposed periphery. Pending further investigation it is proposed 

 to provisionally distinguish this type by the title of Colacium multoculata. The 

 possession of a flagellum by the sedentary zooids was amply demonstrated. 



Fam. IV. NOCTILUCID-ffi, S. K. 



Animalcules free-swimming, bounded by a distinct external membrane 

 or cuticle, the contained endoplasm highly vacuolar, forming a variously 

 modified protoplasmic network ; oral aperture distinct, associated with a 

 single vibratile flagellum, to which may be added a prolonged tentaculiform 

 appendage. Habits pelagic, often phosphorescent. 



Professor Haeckel* has proposed to elevate the most prominent and, up to within 

 a comparatively recent date, only known generic form referable to the present family 

 group, to the rank of a separate order of the Protozoa, or rather of his so-called 

 " Protista, " to be designated the Cysto-Flagellata. The affinities of the type in 

 question, Noctiluca, with the more ordinary representatives of the Stomatode Flagel- 

 lata are, however, so obvious that any such isolation of it cannot be consistently 

 maintained. A closely identical reticulate character of the endoplasmic layer, chiefly 

 distinctive of this form, is met with among various ciliate and flagellate Infusorial 

 types, including such genera as Trachelius, Loxodes, and Callodicfyo/i, while the non- 

 essentiality of the caudiform tentaculate appendage is demonstrated by its entire 

 absence in Hertwig's recently discovered and closely allied genus Lcptodiscus. 



* ' Naturliche Schopfungsgeschichte,' Berlin, 1868. 



