290 Memoirs of the Indian Museum. [Vol.. I, 



In regard to the structure of the organ itself. For almost its entire length the 

 tube is imperfectly divided into a right and left half by a thin membranous partition 

 springing in places from the dorsal in places from the ventral wall. The cells on the 

 surface of this partition are the parent cells of the spermatozoa. The latter consist of 

 apparently naked nuclei of the shape of a peg-top. From the pointed end a small 

 fiagellum projects. They stain very intensely with hsematoxylin. They are found 

 in very large numbers, completely filling the cavity of the gonocœl. 



Nkphridia. (PI. xxi, fig. 9.) 



The nephridia are a pair of branching tubes which open by a single pore at the 

 edge of the shield in the mid- ventral line and extend forward in the ccelom for |^th of 

 the body-length, one on each side of the mid-line. Each tube divides into three 

 branches. They lie in the dorsal cœlomic compartment, between the gill-chamber 

 and the hindgut dorsally, and the liver ventrally. A communication with the cœlom 

 has not been found. 



Histologically they are made up of a columnar epithelium, the cells of which 

 exhibit large vacuoles at their free margin. The vacuolated portion of the cell 

 breaks off into the lumen of the nephridium. This state of affairs is practically 

 identical with that described by Shipley in Phymosoma varians [10]. 



Systematic position. 



There does not appear to be any reasonable objection to the claims of Investiga- 

 tor sicarius to the name Geph^'-rean. The general shape of the body, the existence of 

 an introvert, the character of the spines, the absence of segmentation, the presence 

 of a large cœlom, and the single pair of nephridia are strong proofs. The only fact 

 which would count against this contention is the absence of the ventral nerve cord 

 and the fact that its place is taken by two ventro-lateral cords. But although this 

 must be regarded as a highly important character, it is probably in this case a fairly 

 late modification and certainly not above ordinal value. If it were an early modifi- 

 cation and above ordinal value the resemblances to the Gephyreans detailed above 

 could hardly be so marked. It is not of such importance as in the case of, e.g., the 

 Nemertines. 



Within the Phylum, Investigator most closely approaches the Priapuloidea. 

 The anus and the nephridial pore are situated close to the posterior end of the body. 

 The only important difference is the difference in the nervous system. 



The following addition to the Phylum Gephyrea is therefore proposed : — 



Order INVESTIGATOROIDEA. 



Gephyrea with anterior terminal mouth and posterior sub-terminal anus, with a 

 nervous system consisting of dorsal cerebral ganglia and two lateral nerve cords. 



