234 STROPHOIVIENIA AGASSIZI. 



sense organ. In the present case a nerve arises from the suprarectal commissure, 

 on each side of the body near each lateral ganglion. These two nerves extend 

 dorsally then posteriorly and a short distance in front of the more anterior 

 sense organ they unite to form a single fibre that may be traced, without especial 

 difficulty to the base of the organ. The nerve to the posterior organ arises from 

 the lateral cord, on the left side only, behind the suprarectal commissure and 

 making its way across the visceral ca^^ty it finally comes into close contact 

 with the body wall yet may be distinctly followed to the organ in question. 



^Miether iimervation from one nerve or two is the more primitive, it is 

 impossible to say at present, but it certainlj^ appears to be a fact that such an 

 asymmetrical innervation, as in the case of the posterior organ, indicates that 

 it is either an abnormaUty or is from a phylogenetic standpoint a late formation. 



"\Miile the presence of copulatory spines and seminal receptacles, filled with 

 sperms, have led to the conviction that copulation takes place among the neo- 

 menians no actual example has been noted up to the present time. Definite 

 proof, however, is now at hand, for two indi^'iduals from Sta. 2046 were in the 

 act of copulating (Plate 1, fig. 1). Their posterior extremities were in contact 

 so that the cloacal openings were opposite each other, thus placing the two cham- 

 bers in direct communication with each other, and a whitish secretion appears 

 to have aided the attachment in Ufe, or at all events to have prevented the loss 

 of sperms during the copulatory process. It was thought best not to destroj' 

 these specimens so that nothing is known regarding the course pursued by the 

 sperms on their way to the seminal receptacles nor of the appearance of the 

 organs most intimately concerned in the process. 



In the sectioned specimen several eggs are present in the pericardial ca^^ty 

 and other indications suggest that the egg-laying season was at its height. 

 Fully formed ova are in the gonad along with multitudes of sperms in aU stages 

 of development, and the canals leading from the pericardial ca\'ity are of verj^ 

 large size. In common -nith the other species of the genus the pericardium is 

 spacious and the coelomoducts, lea\ang its postero-lateral borders, are of unusu- 

 ally large calibre. As may be seen (Plate 1, fig. 5) the dorsal limb of each canal 

 is externally a simple urmiodified tube uniting with the shell gland close to its 

 anterior extremity. 



In close proximity to the pericardial opening there is a small, short ridge 

 of cells of larger size than those adjoining and the nuclei are correspondingly 

 large and the cilia longer. This soon disappears and the cells throughout the 

 dorsal Umb are Hghtly staining, cubical, or low columnar, ciUated, and possess 



