ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 563 



month. It is to be regarded as a remnant of a thyroid duct. In the 

 basihyal of Scyllium canicula and S. catulus there is a small foramen, 

 and gland follicles like those of thyroid may occur in it. Perhaps 

 the foramen marks the situation of the anterior end of the original 

 evagination of the thyroid from the ventral wall of the oral cavity. 

 The author recalls the fact that the thyro-glossal duct occasionally 

 persists as an abnormality in man. 



Rearing Marine Larvae.*— E. J. Allen and E. W. Nelson have 

 made numerous experiments on the culture of plankton organisms 

 (especially Diatoms) and on the rearing of marine larvae (sea-urchins, 

 Polychaets, molluscs, etc.). We give their summary of the precautions 

 to be taken in rearing larvae. 



The eggs of the female selected must be really ripe, and the 

 spermatozoa of the male active. The smallest quantity of sperm 

 necessary to fertilize the eggs should be used. Sterile sea-water, 

 treated in such a way that Diatoms, etc., will grow well in it, should be 

 used. No frequent change of water is then necessary. 



All dishes, jars, instruments and pipettes should be carefully sterilized 

 before use. Every possible effort should be made to prevent the in- 

 troduction into the rearing-jars of any organisms other than the larvae 

 to be reared and organisms on which they feed. The jars should be 

 covered with loosely-fitting glass covers. The eggs after fertilization 

 must be separated from all foreign matter, pieces of ovary, or testis, etc. 

 As soon as the larvae swim up they should be pipetted off into fresh 

 vessels of treated water, so as to leave behind any unsegmented 

 eggs, etc. 



The food organisms should be small in size, so that the larvae can 

 draw them into the mouth by ciliary currents. The food should dis- 

 tribute itself through the body of the liquid, and not settle too readily 

 on the bottom of the vessel. (This is one of the great advantages of 

 the Diatom Nitzschia closterium, forma minutissima.) 



The food should be abundant early, so that the larvae may commence 

 feeding as soon as they are able to do so. The food, however, must not 

 be allowed to get excessively thick in the water. It can be kept down 

 by diminishing the light or by changing some of the water. The 

 temperature should be kept as constant as possible. Within limits, the 

 actual degree of temperature is not so important as the avoidance of 

 rapid change of temperature. A good north light, not exposed to direct 

 sunlight, is most suitable for the rearing-jars. 



In determining the amount of water to be used in any particular 

 vessel, regard must be had to the amount of water surface exposed to the- 

 air, which should be large in proportion to the volume of the water. A 

 change of food is generally required after the metamorphosis of the 

 larvae. 



Zoology of the Minotaur Myth.f — C Keller gives a learned dis- 

 cussion of the extinct fauna of Crete, in the course of which he argues 

 ingeniously that Minotaur is a synonym for Bos primigenius. 



* Journ. Biol. Assoc, viii. (1910) pp. 421-74. 



t Viert. Nat. Ges. Zurich, liv. (1909) pp. 424-35. 



