15 



teclmieally by the titles of tlie "germiDal vesicle" and "germinal spot" or the "nucleus" and "nucleolus." 

 Shortly after fertilisation the substance of the ovum becomes opaquel)"- granular throughout, and the 

 germinal vesicle is no longer visible. Within the second hour a sirall globular protuberance will have 

 made its appearance at the broader end of the ovum, and opposite to the micropyle. This is the so-called 

 directive or polar cell. Quickly following upon this, the entire body-mabs of the ovum becomes furrowed 

 or constricted across the centre, and each half is seen to contain a central nucleus. The upper half, 

 associated with the polar cell, now divides itself into two equal parts. These again split into four and 

 next into eight, the aspect of the ovum or embryo, as it nia}"^ now be correctly termed, at about the end 

 of the third hour being that of a number of small coherent cells, superimposed symmetrically on the top 

 of a large basal cell. 



This condition of development represents an important phase in the life history of the embryo 

 oyster. There are now present all the essential elements out of which the perfect animal will be built 

 up. Out of the smaller superincumbent cells all the investing membranes, tactile organs, and essential 

 animal structures will be fashioned, and they are consequently distinguished as the formative cells. The 

 larger basal cell, on the other hand, represents the nutritive or vegetable element, out of which will be 

 constructed the stomach, alimentary track, and all the appended viscera. Within from four to siz hours 

 the smaller or formative cells have so increased and spread as to completely enclose the large nutritive 

 cell, and which in its turn now divides up and lays the foundation of the alimentary track. Fine hair- 

 like cilia are at this stage developed upon the external surface of the embryo, and by means of which it 

 progresses through the water in an irregular rotatory manner. The polar cell, which up to this stage 

 had occupied a conspicuous position, now breaks loose and disappears. The metamorphoses from this 

 point progress more slowly. From the tenth to about the fifteenth hour the general shape of the embryo 

 is somewhat kidney or turban shaped, it having a slight depression on one side. This represents what is 

 known to biologists as the gastrula stage, a structural phase which lias been found to be common to some 

 period in the development history of almost every known form of animal life higher than the unicellular 

 protozoa. In its most typical condition this gastrula embryo consists of a cup-.shaped body composed 

 of two single cell layers, the outer being huilt up of the animal or formative cells, and the inner one out 

 of the nutritive or vegetable cells. The distinctive appellations of the " epiblast" and " hypoblast" are 

 more commonly applied by biologists to these respective outer and inner cell layers. 



After passing the " gastrula " stage, development towards the typical organisation of the parent 

 oyster proceeds apace. The central cavity representing the stomach opens out by an anterior and a 

 posterior passage and apertures, which correspond respectively with the throat and mouth, and the 

 intestine and vent. The shells make their appearance at a depression in the dorsal surface, and gradually 

 increase in size until they enclose the entire body. Simultaneously with these metamorphoses a disc 

 covered with poweiful vibratile cilia has developed at the anterior extremity, and with the assistance of 

 which the embryo oyster can propel itself vigorously through the water. As the shells grow larger and 

 heavier the little oyster becomes less capable of sustaining itself in the water, and finally sinks to the 

 bottom. This is a crucial jieoch in the mollusc's existence. Should it settle upon a rock, shell, or other 

 clean, hard substance, it attaches itself to it, and its life is assured; but should it, on the contrary, li£;ht 

 upon soft mud, sand, or other material to which it cannot adhere, it inevitably perishes. The proportion 

 of young oysters that find a secure anchorage in comparison with the vast numbers that are devoured, or 

 become literally lost at sea, is necessarily infinitesimal. 



The time taken by the embryo of the Australian oyster to pass through the series of metamorphoses 

 enumerated, and to arrive at the attached or sedentary state, has been found by me, under favourable 

 conditions, to average four days, two out of these elapsing before the shells become conspicuously 

 apparent. 



Within from eighteen months to three years from the date of its birth the embryo becomes a 

 marketable oyster measuring the standard two inches in its longest diameter. Such, however, is the 

 precocity of the species that, oyster brood not more than three months old, and but half an inch in 

 diameter was found, in association with the foregoing embryological investigations, to be laden with 

 fully-matured ova and milt. 



Drawings made with the aid of the microscope of all the leading developmental phases of Ostrea 

 glomerata, as described in the foregoing communication, are reproduced in Plate IX. of this report. 

 Some further experiments that were conducted in association with these embryological investigations with 

 the object of ascertaining the influence of water of varying density, as in time of floods, upon this 

 embryonic oyster brood have been referred to at page 7. Among the practical results suggested 

 in connection with the foregoing embryological data here recorded, is the feasibility of fertilising and 

 artificially propagating the embryos of Ostrea glomerata in numbers largely in excess of what is accomplished 

 in a state of nature. In Europe, where the demand is so much in excess of the supply, and the market 

 prices consequently higher, and also in America, much attention is being given to the problem of thus 

 successfully cultivating oysters from their earliest embryonic state. By such time as this supply and 

 demand shall be equivalently balanced 11 ;';e Australian market, a resort to this supplementary method of 

 artificial fertilisation and propagation may be found profitable. 



Details of Aeeas Reserved ob Leased foe Ovstee Cuituee i.^ Queensland Watees, with 

 Eetuen of Quantities and Value of Oystees Expoeted. 



The areas devoted to the industry of oyster culture in Queensland waters fall under the three 

 separate categories of dredge sections, oyster banks, and oyster grounds. Under the first-named title are 

 included extensive water areas producing dredge oysters only, and not extending shorewards above the 

 limit of low-water mark. These areas are leased by auction for terms of fourteen years to the highest bidder. 

 The waters of Moreton Bay were originrdly subdivided into forty-two such sections. The value of certain 

 of the more productive of these sections may be gauged by the fact that the rental realised for one of the 

 more important ones when recently put up to public auction was no less than £1,000 per annum. 

 Within the term of " oyster banks " are included all oyster-bearing banks, reefs, or other areas comprised 

 within the limits of high water-mark and two feet below the lowest ebb. For these areas licenses are 

 issued at the uniform rate of £.5 for any such bank not exceeding 30 acres in extent. The total number 

 of banks marked off, according to the latest returns, included in Moreton Bay, is 347, and in Wide Bay 

 1G7. In the Eockhampton district, including Kodd Harbour, Port Curtis, and Keppel Bay, between 



forty 



