156 NEW YORK STATE MUSEUM 



p o r u m has afforded the material for most of the illustrations 

 here given. Of this very common species in the calcareous shales of 

 the Hamilton I have been able to critically examine several hun- 

 dred individuals and it is safe to say that the worm is present in 

 the majority of examples. It is easy to determine its presence on 

 inspection of the tentacular surface of the coral by the contrast 

 between its round tubes and the angular coral cells. All the speci- 

 mens here figured to show the convolutions of the worm have 

 been drawn from actual preparations. 



The history of the combination in P. s t y 1 o p o r u m is as 

 follows: At the close of the free-swimming larval stage the coral, 

 in fully eight cases out of ten, selected and attached itself to a dead 

 or living shell of the gastropod Loxonema hamiltoniae. 

 Directly upon fixation or even actually contemporaneous with it 

 was the attachment of the larval worm upon the incipient coral or 

 alongside it. In many cases, such as that illustrated in plate 4, figure 3 , 

 the worm tube is directly fixed to the gastropod; again it may 

 be. free of the gastropod, and separated from it by the thick- 

 ened basal theca [see pi. 4, fig. i, 2]. ^^ith the multiplication of 

 cell growth and the upward trend of the coral, the worm began 

 its convoluted growth, its tube growing as much at one end 

 as at the other. Some of the existing serpulid worms have 

 their eyes on the hinder end of the body at the tentacular 

 surface; it is fair to presume that at this early period this 

 advanced stage of degeneracy had not been reached and the 

 tube was thus kept open at both ends. In view of the regularity 

 of coiling shown in some of the commensal worm tubes it is 

 interesting to notice that in this case the worm after making 

 a start, gets its double coil into parallelism for a half to an entire 

 turn and then each arm starts off into a direct course follow- 

 ing the radial path of the coral cells. These branches often pass 

 in and out between the cells, keeping their extremities always at 

 the tentacular surface and very seldom is there evidence of the 

 worm encroaching on the polypite cells. Still this may occur and 

 the worm tube occasionally becomes encased by a young polypite 

 and holds a position in the center of the cell [pi. 4, fig. 4]. 



There may be other worms encased in the thickened base of this 

 coral as shown in figures i, 2, plate 4, but it is not yet clear where 

 their apertures lie as I have never seen but two annelid openings at 

 the surface of the adult coral. It is quite possible that originally 

 opening on the tentacular surface at an early stage of coral growth 



