Anatomij of certain Rotifers. 4o 



canals in Lacinularia socialis to which I think sufficient 

 attention has not been hitherto directed. Placed within the 

 ciliary wreath or corona, on either side of the oral aperture, is 

 a dilated portion of the lateral canals. A continuation of 

 the lateral canal extends over the mouth, and joins the corre- 

 sponding dilatation on the other side. Concerning this 

 dilated portion of the lateral canals Prof. Huxlej ( 5) says in a 

 footnote as follows : — " The only discrepancy of importance 

 in Leydig^s account is, firstly, that he considers what I have 

 called the 'vacuolar thickening on each side of the pharyn- 

 geal mass,' and what Ehrenberg calls a nervous centre, to be 

 formed by convolutions of the water-vessel itself . . . Leydig 

 does not seem to have noticed the transverse anastomosing 

 vessel over the pharynx." 



After a careful study of my sections through these dilated 

 portions of the lateral canals I believe their structure to be 

 as follows : — On reference to PI. V. fig. 11 and the explanation 

 accompanying it the course of a lateral canal can be easily 

 traced for some considerable distance in the dilated portion, 

 and then suddenly terminates. As to whether or no there is 

 a ciliated opening at the point where the canal abruptly 

 terminates I am unable to satisfy myself. Be this as it may, 

 the tube continues, and, uniting with the transverse branch, 

 runs over the ganglion and unites with its fellow on the 

 opposite side. The character of the tissue which surrounds 

 these convoluted tubes appears to be of a spongy nature with 

 scattered nuclei [vide figs. 11 and 12). As to whether or no 

 actual secretion takes place in this region, I am unable at 

 present to determine. 



As to whether or no the lateral canals finally open into the 

 cloaca or possess a separate opening to the exterior, inves- 

 tigators have concerning this point differed greatly in opinion. 

 Prof. Huxley says : " There is no contractile sac opening into 

 the cloaca as in other genera, but two very delicate vessels, 

 about l-4000th of an inch in diameter, clear and colourless, 

 arise by a common origin upon the dorsal side of the intes- 

 tine. Whether they open into this, or have a distinct external 

 duct, I cannot say." L)r. Hudson, after giving a short sum- 

 mary of Prof. Huxley's remarks, says : — ^' . . . but Dr. 

 Leydig says that the lateral canals start from a common 

 branch opening into a contractile vesicle, which discharges 

 itself into the cloaca : it will be seen that a similar doubt 

 exists concerning the termination of the canals in Conochilus 

 volvox, and further investigation is, I think, wanted to make 

 the matter clear." 



After examining many dozens of sections taken through 



