122 THE KOTIFEEA. 



and having a ciliated opening. It can be drawn back by two pairs of muscles attached to 

 the dorsal surface. Short muscular threads help to draw and direct it forward ; but its 

 vigorous outward movement is mainly due to the compression of the body-fluids by 

 transverse muscles. The spermatozoa can be distinctly seen in motion in the sperm-sac, 

 and they are of the two forms drawn in fig. 3&. The vascular system (fig. 3/) is alike 

 in both sexes, but is much better seen in the male. The flocculent ribbons which 

 support the lateral canals are unusually large and long, and are looped up here and 

 there by threads, and also tied in the same way to the body-walls. They appear, them- 

 selves, to be tubes of a loose granular stuff, with clear cells (fig. 3g) imbedded in their 

 walls. Possibly it is through these cells that the perivisceral fluid finds its way into 

 the tubes and thence into the lateral canals. These latter are much smaller tubes, con- 

 nected with the first, but meandering along their edge ; and they have attached to them an 

 amazing number of vibratile tags ; often more than forty on either side. The contractile 

 vesicle, to which the flocculent ribbons and lateral canals are obviously attached, swells 

 out in the female, at times, so as to occupy nearly two-thirds of the body. In the male 

 it is smaller, but in both sexes it is covered with a fine muscular network, which is con- 

 stantly compressing it into ever-varying and graceful shapes. The muscular system is 

 best seen in the male, owing to the absence of digestive organs, but is so plainly shown 

 in the drawings that it requires no further explanation. 



Length. Nearly ^ inch. Habitat. Ebbesborne Wake, Wiltshire (Mrs. Tupper 

 Carey) : very rare. 



A. BIUGHTWELLII, Gosse. 

 (PI. XII. fig. 1.) 



A dicecious rotifer allied to the genus Notommata . . Brightwell, Ann. Nat. Hist. 2 Ser. vol. ii. 



1848, p. 153, pi. vi. 

 An infusory animalcule allied to tlie genus Notommata . Dalrymple, Phil. Trans. 1849, p. 331, pis. 



xxxiii. xxxiv. 

 Asplanchna Brightwellii and A. Bowesii . . . . Gosse, Ann. Nat. Hist. 2 Ser. vol. vi. 



1850, p. 23. 

 Ascomorpha Anglica Perty, Zur Kenntniss kleinst. Lebensf. 



1852, p. 39. 



SP. CH. Female without humps ; eye single; rami with doubly pointed ends, not 

 serrated; contractile vesicle expanding to about one-fourth of body -cavity ; vibratile 

 tags on each side varying from about ten to tiuenty, and arranged in a straight line; ovary 

 horseshoe-shaped; male without humps. 



Mr. Brightwell discovered this species in a small pond immediately without the city 

 of Norwich in 1841. Both sexes were in abundance, so that he was able not only to 

 make out the structure of the male, but also to witness several acts of copulation ; thus, 

 for the first time, establishing beyond all question the dioecious character of at least one 

 species of the Eotifera. The female differs from that of A. Ebbesbornii in the following 

 points. It is bell-shaped, possessing none of those humps which are so striking a feature 

 in the former species. The jaws (fig. 1b) differ slightly in their proportions and shape, 

 and Mr. Dalrymple (loc. cit.) detected on either side of the stout rami delicate curved 

 rods, which no doubt are the unci. The gastric glands are kidney-shaped, the contrac- 

 tile vesicle somewhat smaller. The ephippial egg of this species is also circular, but it 

 has on its outer covering a beautiful pattern of concentric circles of overlapping scales. 

 The male (fig. Ic) is also humpless, but it is a little squarer in outline behind than the 

 female, from the ventral surface having been produced into a sheath for the penis. 1 



Length. Female, ^ f inch ; male, V inch. Habitat. Ponds and ditches in many 

 parts of England : not uncommon. 



1 In 1874 I found an Asplanchna apparently not distinguishable from A. Brightwellii, and whose 

 male (Mon. Micr. J. pi. xci.) had only two lateral humps. Mr. T. Bolton has lately found both sexes 

 near Birmingham. I have named it provisionally A. intermedia. 



