OF THE ROTATORIA. 461 



cases, the examination of a species has been casually undertaken ; the attention 

 has been directed to it only by some accidental cii'cumstances, and this only on 

 some one occasion. We cannot, therefore,wonder that the rarely-occurring males 

 have not often been encountered. But the most satisfactory means of deter- 

 mining the existence and characters of the males of any species of Eotatoria 

 have latterly been furnished by the careful descriptions of the special cha- 

 racteristics of male ova, whereby they can be distinguished even before leaving 

 the oviduct, and their develoi^mental history traced forwards until their ma- 

 turity. 



AYe may mention that 'Mi\ HaUett, formerly demonstrator of anatomy in 

 the University of Edinburgh, and subsequently a student in anatomy at the 

 College of Surgeons, London, directed his special attention for many years to 

 the Eotatoria, and especially to the detection of the male individuals ; and 

 although his early death has deprived naturalists of the published results of 

 his researches, yet, from repeated verbal communication, we can state that 

 he had arrived at the discovery of the male beings of the majority of the 

 Eotatoria. 



Doubtful Male Organs. — Many natui'alists are unprepared to admit bi- 

 sexuahty to be the universal rule in Eotatoria ; and several eminent observers 

 are disposed to consider certain organs in female animals to be of a male 

 sexual character. 



Prof. Williamson, in his liistoiy of MeJicerta, says — " I have sought in 

 vain for any organ to which the functions of a spermatic gland can be indis- 

 putably assigned. Immediately beneath the lower stomach and the conti- 

 guous oviduct, there is an elongated pyramidal organ, apparently hollow, the 

 thick extremity of which is directed towards the ovary, and its opposite at- 

 tenuated portion passes upwards towards the cloaca, between the oviduct and 

 the general integument. Into the thick inferior extremity of this organ, 

 there are inserted, exactly opposite to each other, two long-cylindiical ap- 

 pendages, which diverge, and, passing on each side of the alimentary canal, 

 proceed towards the upper part of the body, where their extremities are not 

 easily traced. In but one instance I observed them to terminate in a series 

 of irregular convolutions near the base of the two tentacles. Though not yet 

 capable of demonstration, it appears probable that this curious appendage 

 may be a filamentous spermatic tube resembling those found in many Arti- 

 culata. That they are tubes, and not muscular bands, appears unquestionable ; 

 and as they have obviously a direct connexion with the cloaca, they might 

 easily discharge a fertilizing secretion into that common excretory canal, from 

 which it would find its way to the ovary through the oviduct" (p. 432). 



Now it is to be remarked that Mr. Williamson states he could discover 

 " no special organs of circulation or respiration, no vessels or pulsating 

 organs," and that the two tubes he has referred to as being possibly sper- 

 matic ducts are the homologues of similar ones in other Eotifera, to which 

 Ehrenberg has assigned fertilizing functions. Further on he observes — 

 " The singular bodies resembling spermatozoa exist in various parts of the 

 organism, where they are apparently enclosed within hollow canals. I have 

 never seen them occupying the two main trunks of the 'water-vascular 

 system ' or cseca ; nor can I succeed in tracing any connexion between them. 

 In several cases I have seen one or two of these curious bodies opposite the 

 centre of the upper stomach, very near to, but independent of, the main csecal 

 canal, and at some distance below the point where the latter probably sub- 

 divides into branches. Near the neck there are usually from two to three 

 pairs. Their vibratilc motion ceases the moment the animal is killed by 

 pressure. This fact does not countenance the idea that they are spermatozoa." 



