ROTIFERA. 51 



in the Rotifera ; and lastly, neither the pulsatile sac nor the slender la- 

 teral canals ever contain spermatozoa. The conclusion to which Siebold 

 arrived, viz., that only female organs could be determined in the large 

 and complex Rotifera, which had been examined by him and others, 

 appeared, therefore, to be well-founded. At this stage of know- 

 ledge of the nature of the generation of Rotifera, the following ob- 

 servations were very timely and acceptable. Mr. Brightwell, who 

 has paid much attention to the Infusoria, and has published a work 

 on those found in the county of Norfolk, met with some small 

 individuals of a species of Notommata, so different in character to the 

 ordinary large female ones, to which they were often attached, as to 

 give him the impression that they were the male individuals*; and 

 in a letter which I have received from him he says : " I have lately 

 repeatedly seen the male in connexion with the female ; and it re- 

 mains so for about seventy seconds." In these small individuals 

 Mr. Dalrymple has discovered organs with abundant spermatozoa ; 

 but the rest of their structure is much more simple than that of the 

 female : e. g. they have neither intestine nor anus. This may seem 

 at first opposed to all ordinary analogies ; but inferiority, not of size 

 only, but in grade of organization, is no uncommon characteristic of 

 the male in the invertebrate series. Nordmann discovered the male 

 of the Lernaea to be a minute parasite upon the vulva of the female. 

 Darwin has detected an analogous condition of the impregnating 

 individual in certain Cirripedes ; and the worm which Cuvier de- 

 scribed under the name of the Hectocolylus, as the parasite of the 

 Argonaut, appears from the observations of the accurate Kolliker, to 

 be actually the male of that species. 



In the Notommata Syrinx the male is about half the size of the 

 female : it has a large round sperm-sac, or testis, at the lower end of 

 its body, communicating by a short duct with a short penis or sperm- 

 tube. The spermatozoa may be seen in active motion within the sperm- 

 sac. On the 15th of June Mr. Brightwell f placed one of these males 

 and six females in a small glass trough, and on the following day saw 

 it attach itself to a female by his sperm-tube, remaining so attached 

 twenty or thirty seconds : it afterwards repeated the act with four 

 other females : the whole occupying a period of about fifteen minutes. 

 Mr. Gosse % has subsequently recognised similar males in the genus 

 Asplaiichna ; and Dr. Leydig has described from one to four indi- 

 viduals in each colony of LacinularicB §, which exclusively develope 

 spermatozoa : but he recognises in these the ovarium also, and believes 

 them to be hermaphrodites, whilst the rest are females. There can 



* XXXVII. p. 153. fXXXVII. p. 17. J XXXVI. p. 22. § XXXV*. p. 47 L 



F -2 



