DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 667 



ovum, may be transient and give place after extrusion to an imperfect transparency. 

 The ova of Ammodytes tobianus present a marked example of this, for while contained in 

 the ovary they are of a bright orange colour — the ovaries on this account forming a 

 bilobed orange-tinted mass in the abdomen of the nearly ripe female, but the eggs when 

 ready for extrusion, and indeed while passing to the oviducal aperture, would appear to 

 become colourless. Pelagic eggs usually float loosely together or singly, and do not 

 adhere to each other, save in certain noticeable instances, of which Lophius piscatorius is 

 an interesting example. Agassiz first described the floating eggs of this familiar fish as 

 adhering together in long bands near the surface (No. 1, p. 280), but even in this case 

 eggs may become detached and float free (No. 2, p. 16). Professor E. van Beneden 

 describes some minute isolated and agglutinated eggs which he was not able to deter- 

 mine, but believed that they belonged to a species of Lota, and he supposed that, after 

 being deposited in a mass, they " remain for some time adherent one to another, and 

 afterwards separate, and then float free from all adhesion, on the surface of the sea " 

 (No. 25, p. 41). This surmise is perhaps questionable, and Van Beneden, indeed, himself 

 adds — " I never saw the eggs become detached from one another" (p. 42); and they prob- 

 ably, therefore, belonged to two different species. Eggs similar to those of E. van Beneden 

 were obtained by Haeckel on the coast of Corsica. They formed agglutinated masses of 

 various volume and form — the ova being in fact imbedded in a gelatinous substance. * 

 Pelagic ova, if ever adherent, possibly may soon become detached, but eggs deposited on 

 the sea-bottom, in masses, adhere together most strongly, though in an advanced stage 

 they are less firmly united, this loss of adherent property in such a form as Cyclopterus 

 lumpus taking place only after the lapse of a considerable interval, often many weeks, 

 when the capsule becomes softened, and changes occur in its physical character, probably 

 to facilitate the liberation of the contained embryo. Usually, however, these eggs cling 

 together if undisturbed (even when dead) for long periods. The adhesive character 

 which Von Baer was the first to notice in certain Cyprinoidst is due to a mucilaginous 

 ovarian secretion bathing the eggs, and acting as a lubricant during extrusion. On 

 exposure to water, it has the property of hardening, as in many similar instances both in 

 vertebrates and invertebrates ; and, in the case of adherent eggs, it acts as a cement, bind- 

 ing them together so firmly that they can be separated only with difficulty ; and the points 

 where the adjacent eggs were in contact show prominent scars or facets after separation 

 (PI. I. figs. 2, 3, and 4, x). 



A marked translucency of both capsule and egg-contents usually indicates the healthy 



* Mr Rattray has recently submitted to us examples of pelagic ova from the west coast of Africa, which are also 

 bound in masses by a connecting substance converted by reagents and alcohol into a thread-like meshwork. Threads 

 of a like character were noticed in some ova sent by M. Millet many years ago to the French Academy of Sciences. 

 They were evidently demersal eggs, for they were attached to a wooden barrel hoop by the elastic threads, the latter 

 forming a felted meshwork, which Millet supposed to be produced by the parent-fish (No. 110, p. 342). They were 

 procured in 14° 15' N. lat. and 20° 30' W. long. The eggs Mr Rattray kindly sent to St Andrews were obtained (in the 

 s.s. " Buccaneer " Expedition) in lat. 1° 17' 6" N., long. 13° 54' 4" W. Vide Remarks on these by Mr J. T. Cunningham, 

 Trans. Roy. Soc. Edin., xxxiii. i. p. 108, pi. vii. fig. 7. 



+ Untersuchuncjen iiber die Entvjickelungsgeschichte der Fische, Leipzig, 1835, p. 7. 



