TRANSACTIONS OP SECTION D. 407 



FRIDAY, SEPT EM HER 1. 

 The following Papers and Reports were read : — 



1. On a new Gymnoblastic Hydroid (Ichthyocodium sarcotretis), epizoic 

 on a new Parasitic Copepod (Sarcotretes scopeli) infesting Scopelus 

 glacialis (Rhos.). By Hector F. B. Jungersen. 



(i) The Hydroid coats more or less of the external part of a Parasitic 

 Copepod deeply sunk into the body of Scopelus glacialis. It consists of (1) 

 Polypes devoid of tentacles and growing from a network of delicate tubes 

 enclosed in a basal membrane without perisarc; (2) Medusa-buds arising from 

 the base of the Polypes. The largest buds possess a bell with two marginal ten- 

 tacles and four simple radial canals; the manubrium is distinct; when fully 

 developed they are set free as Medusre (Anthomedusa;). This new Hydroid is 

 related to Hydrichthys mirus (Fewkes), epizoic on the fish Seriola zonata, and 

 has to be adopted into the family of Corynidce as defined by Stechow (1909). 



(ii) The Parasitic Copepod Sarcotretes scopeli represents a new genus and 

 species of the family Lernceidcc, allied to genera like Peroderma Lernaenicus, 

 Lernoea, Pamella. The adult female has an elongated body ; the middle part of 

 the long genital segment is constricted into a narrow, firmly chitinised stalk ; 

 only the distal, claviform part behind the stalk protrudes outside the host. 

 Cephalothorax with the dorsal shield fully preserved; two large clumsy out- 

 growths arise below the margins of the shield ; no other outgrowths are present. 

 The antennules are linear, the antenme cheliform, the sipho large; one pair of 

 maxillipeds ; three pairs of abdominal feet, the two anterior biramous, the pos- 

 terior uniramous; three free abdominal segments with well-developed tergal and 

 sternal parts. It is found in the eastern part of the Atlantic, inserted into the 

 body of Scopelus glacialis, the body-wall of which it pierces, penetrating to the 

 alimentary tract. 



On the same species of fish has been found a series of its Metamorphosis- 

 stages : (1) A Cyclops-stage, resembling that of Lerncca branchialis , capable of 

 moving along on the host and attaching itself by its strong cheliform antennne ; 

 (2) Four Pupa-stages, passively fixed to their host by means of a hardened secre- 

 tion from the rostrum. 



Inside the last Pupa the copulatory form has been observed. The copulatory 

 form probably lives for a while in a free state. After impregnation the female 

 takes up the parasitic life anew, but in a more intense form : it pierces the skin 

 of a Scopelus glacialis, and, gradually growing, it penetrates through the muscles 

 and reaches by and by the intestines of the host. 



The triple association between the Fish, the Copepod, and the Hydroid seems 

 to be a regular one : of fourteen adult Sarcotretes seven carry the Ichthyocodium , 

 and the loss of tentacles in the Polypes of the latter seems to show that the 

 Hydroid in some way or other depends on the fish for getting its food. 



2. On the Species of the Genus Balanus collected in the Malay Archipelago 

 during the Cruise of the Dutch Man-of-war ' Siboga. , By Dr. P. P. C. 

 Hoek. 



The Archipelago is very rich in forms of this genus. Darwin, whose most 

 excellent monograph remains the standard work for the group Cirripedia (and, 1 

 might say, for the difficult genus Balanus especially), knew and described (1854) 

 forty-five of its species, thirty-nine of which are living species, six found fossil 

 only. Sixteen of the living species, according to Darwin, live in the Malay Archi- 

 pelago and surrounding seas (coast of Bengal, Ceylon, Australia), and this 

 number has but slightly increased since the appearance of his book; taking 

 the region in somewhat extended form, the whole number of species known to 

 occur there at present can be estimated as twenty-five at most. 



In the collections made by Professor Weber during the cruise of the 

 1 Siboga,' the genus Balanus was found to be represented by twenty-seven 



