13 



It appears desirable for me to mention here that the fears that have been expressed in some 

 quarters lest the disease under notice should be inlroduced with the worm from New South Wales are, 

 in my opinion, altogether groundless. As a matter of fact L/'/icudore is already here; it is of cosmopolitan 

 distribution, and has been obtained by me among the coral reefs as far nortn as Torres Straits. So long 

 as the oyster banks of Queensland are maintained in a clean and healthy state, the worm is not likely to 

 invade them. So soon, however, as these become clioked with foul mud and sedimentary deposits, the 

 conditions will be made favourable for the advent of the worm, and it may most assuredly be expected. 

 While thus enjoying present immunity from the worm disease, which has wrought so much havoc to the 

 oyster fisheries of a neighbouring colony, there are circumstances, subject to the control of human agency, 

 which might arise and exert a very serious if not quite as disastrous an influeuce as those of Moreton 

 Bay. Eeference is here made to the effects that would probably ensue through the establishment on the 

 Brisbane or other tributary rivers, on an extensive scale, of chemical works or factories without restrictions 

 being placed on the discharge into their waters of noxious fluids or other deleterious matters. At 

 present but a few of such factories exist, and comparatively little harm is caused, though already the 

 destruction of fish through such polluting agencies is now and again reported With a multiplication of 

 such pollution-creating factories, there can be no doubt that the effects would be serious to both the 

 oyster and the general fisheries of Moreton Bay, and so many and valuable interests being bound up in 

 these industries, it is highly desirable that measures should be taken in time to safeguard them from all 

 risk of deterioration through such an easily preventable cause. 



There is one other agency at work which, if allowed to continue unchecked, threatens 

 to exert an unfavourable nifluence on the oyster fisheries of Queensland. Under existing regulations 

 what are known as the Government or public oyster reserves are supposed to be retained as breeding 

 centres for the express benefit of the general public, who are permitted to help themselves without restric- 

 tion to such oysters as they can consume on the ground, but are prohibited from carrying them away. 

 This privilege, however, has been abused to such an extent, that on many of the most extensive of these 

 reserves the oysters have been completely stripped and carried off in a wholesale manner. It is, in my 

 opinion, essential for the continued prosperity of the Oyster Fisheries of this Colony that judiciously 

 selected areas should be strictly and permanently reserved as nursery or breeding centres for keeping up 

 the supply of spat. Having regard also to the extent that many of the leased grounds and banks are 

 denuded of their oyster crops without compunction or consideration for future cultivators, it is, I consider, 

 highly desirable that a clause should be included in the leases granted requiring the continual reservation 

 on the ground or bank of a certain proportion of breeding oysters or, at all events, prohibiting their 

 entire removal. With such suggested breeding reserves, efficiently maintained, the Queensland Oyster 

 Fisheries would be well insured against all risk of the injury through over-depletion that has befallen those 

 of certain of the more Southern colonies. At the same time, the foundation would be laid for the develop- 

 ment of this important industry on a more extensive scale than has hitherto been attempted, and for 

 which there is a wide field open, more particularly in the direction of canning and other preservative 

 processes for the export market. 



THE EMBEYOLOGICAL PHENOMENA OP THE QUENSLAND COMMEECIAL Oi'STEE. 



(Osfrea glomerata) . 



Considerable uncertainty having up to a recent date prevailed concerning the embryological 

 phenomena of the ordinary rock oyster of Queensland and New South Wales, I devoted some time last 

 year to the investigation of this subject. The results of these investigations were embodied in a paper 

 communicated by me to the Eoyal Society of Queensland in February of that year, and from which the 

 following account has been epitomised : — 



"The researches that have been already conducted by European and American naturalists, with 

 relation to the commercial oysters of the Northern hemisphere, have elicited the fact that the fertilisation 

 and development of the oyster brood or spat is formulated on two essentially distinct plans. In the 

 case of the most familiar European type, Ostrea eJulis, represented by the far-famed British native and the 

 variety so extensively cultivated on the coast of France, the propagation of the species is accompanied by 

 a condition in which the oyster is unfit for consumption, and is prohibited to be sold. This is occasioned 

 through the circumstance that the parent oyster nurses or incubates its brood within the pallial or mantle 

 cavity, throughout the early stages of its development, and does not liberate it until the shells of the 

 young oysters are fully formed. An oyster eaten during the later phases of the breeding season 

 appears to be full of sand or grit, this being due to the presence of the many millions of minute 

 embryonic shells. By oyster dealers at home, two distinct spawning conditions of the oyster are recog- 

 nised : the one, when the embryos contained within the mantle chambers of the parent are white and 

 colourless, being devoid of shells, is designated the ' white sickness.' The later stage, when, the 

 sheila being formed, a grey or blackish tint is imparted to the entire mass, is known as the ' black sick- 

 ness.' The close or spawning sca.sjii of the ordinary European oyster, Ostrea edulis, extends through- 

 out the summer, from May to September, and is popularly defined as represented by those months 

 in which the letter ' r ' is absent. 



" The fecundation of the ova of the European oyster necessarily takes places within the mantle- 

 cavity or brood-chambers of the female, the fertilising fluid or milt of the male being discharged into the 

 water, and from thence it is absorbed and brought into contact with the mature ova by the ciliary 

 currents that exercise the ordinary respiratory and food-purveying functions in the female mollusc. This 

 plan of propagation was until within recent years supposed to apply to all descriptions of oysters. 

 Investigations associated with the reproductive phenomena of the American commercial oyster, Ostrea 

 virgineana, failed, however, to discover any trace of the brood or spat within the mantle cavities of the 

 breeding oyster, and it was ultimately demonstrated by Dr. Brooks (18S0) that both the ova and milt 

 were simultaneously discharged into the water in their mature condition, and fertilisation being there 

 effected, the entire development of the embryo took place independently of the parent. Such being the 

 case, the artificial propagation of the species by the commingling in sea water of the matured sexual 

 elements was considered feasible, and was successfully accomplished by the above-named authority. In 

 the case of the typical European oyster, Ostrea edulis, such a method of artificial propagation is not 



possible, 



