74 HAROLD HEATH. 



these remarkable mutual benefit societies, describing the associa- 

 tion of the hydroid Slylactis minoi with the rock perch, Mhinns 

 inennis. Several specimens wen- taken at depths varying from 

 forty to seventy fathoms in the Hay of Bengal and the Laccadm- 

 or Malabar sea; and in every ca^e the hydroid was found at- 

 tached in large numbers about the gill opening, on the throat 

 and in the axilla. And not only were no fish of this species ever 

 discovered without being coated with the hydroid, but none of 

 these hydroids was ever found upon the multitudes of other 

 animals dredged in the same locality, though among these were 

 specimens of Minous coccineus. Accordingly it thus appears to 

 Alcock that, unusual though it is, this is a case of true com- 

 mensalism. 



Several years later Doflein collected three more specimens of 

 M. inermis in Sagami Bay, Japan, and again all were coated, 

 especially between the pectoral and ventral fins, with this same 

 hydroid. In the first account the coelenterate was assigned by 

 Alcock, on characters associated with the reproductive sacs, to 

 the genus Podocoryne; but other specimens, seemingly more 

 highly developed, led the author later to place them in the genus 

 Stylactis. On the other hand, Stechow, 1 who described the 

 Japanese specimens, finds no evidence of spordsacs, but young 

 medusa 5 with tentacles and four radial canals and accordingly 

 this author places the species once more in the genus Podocoryne. 



During the past summer my friend and colleague, Prof. E. C. 

 Starks, dredged upwards oi a hundred specimens of an agonoid 

 fish, Hypfdgonus quadricornis, in Puget Sound at a depth of 

 approximately forty fathoms. The area over which the dredging 

 extended was in the neighborhood of Friday Harbor and em- 

 braced an area of at least two hundred square miles where the 

 bottom varied from sand to mud. Of the 37 specimens preserved 

 in the Stanford University collection 10 of them are coated with a 

 new species of hydroid, Perigonimus pugetensis, whose descrip- 

 tion is given later. In every specimen the ccelenterate was more 

 abundant on the ventral surface of the body, especially in tin- 

 axilla, and a luxuriant growth was usually found on the pectoral, 

 ventral and, to a less extent, on the anal and caudal fins. With 



'Zoo/. Am., Bd. 32, p. 752, 1908. 



