440 MR. H N. MOSELEY ON THE STRUCTURE OF THE STYLASTERID2E. 
spadix vvi thin the testis, but am not certain. I could not determine from which layer 
the spermatic cells are developed. 
The spermatozoa are developed in the same manner as in other Hydroids. In 
Plate 36, G, is figured the usual mass of small spermatic cells in an unripe testis. 
Above this is a ripe testis which is shown as not cut right through its axis, it being 
bent over a little from the perpendicular to the surface. Hence the spadix is not 
seen in the section. 
The ripe spermatozoa (Plate 43, fig. 12) have conspicuous heads which are elongate 
bodies curved into a bow shape. They are compressed and flattened in the plane of 
the curve, so that though broad and conspicuous when viewed on the flattened sides, 
they appear almost linear when seen on edge. At the extremity of the head where 
the tail is attached, a small rounded vesicle was observed in all cases to be present. 
The bases of the gonophores are continuous with large canals of the ccenosarcal 
mesh work, the endoderm of the spadix being continuous with that of these canals. 
(2.) GENUS PLIOBOTHRUS (POURTALES). 
The genus Pliobothrus was formed by Pourtales (Bull. Mus. Comp. Zool., Cambridge, 
Mass., No. 7) to include specimens dredged by the United States Coast Survey off the 
coast of Florida, in from 100 to 150 fathoms. Pourtales rightly placed the new genus 
amongst the Hydroids, but, judging from the structure of the hard parts alone, associated 
it with Millejoora. Count Pourtales, however, most kindly placed at my disposal 
specimens of Pliobothrus symmetricus preserved in spirit, and in excellent condition ; 
and these have yielded tolerably complete evidence as to the structure of the soft parts. 
Moreover, the two small specimens transmitted to me proved to be of opposite sexes. 
I have observed both sexes only in the case of one other genus of the Stylasteridse, 
namely, Cryptohelia. The structure of the soft parts of Pliobothrus proves the coral 
to belong undoubtedly to the Stylasteridae. The specimens of Pliobothrus symmetricus 
examined by me were dredged off Florida Reef, in 100 to 300 fathoms. 
Corallum of Pliobothrus symmetricus. 
The corallum is described and figured by Pourtales (‘ Deep Sea Corals,’ 111. Cat. 
Mus. Comp. Zool., Harvard Coll , Cambridge, Mass., 1871, p. 57, Plate iv., figs. 7 and 
8). He describes three kinds of pores as existing in the corallum. In reality, there 
are only two kinds of true pores present, viz., the larger circular-mouthed gastropores 
and the smaller dactylopores, which open at the summits of short tubular projections 
from the general surface of the corallum. The third kind of pores is described by 
Pourtales as very small linear disposed over the whole coenenchyma, and arranged in 
rows. These are merely spaces between the trabeculae of hard tissue forming the 
coenenchym of the corallum, and are occupied by canals of the coenosarcal mesliwork 
