2 EMBBYOLOGY OF THE LOWEE VEETEBEATES oh. 



interest as being in bulk the largest single cells known in either the 

 Animal or the Vegetable Kingdom. 



The adjoining list based upon data obtained by various observers 

 — MTntosh and Masterman, Bashford Dean, Boulenger, Budgett, 

 Bles, Semon, Salensky and others — brings out in more detail the 

 differences in the size of the Zygote amongst the lower Vertebrates. 



APPROXIMATE DIAMETER OF EGG (IN MILLIMETRES) 

 OF VARIOUS FISHES AND AMPHIBIANS 



Bothus maximus 1. 

 Pleuronectes platessa 1 • 8. 

 P. microcephalus 1-3. 

 P. limanda -75. 

 Solea vulgaris 1-2. 

 Glupea harengus -9-1. 

 C. sprattus -1. 

 Ceratodus 2-8. 

 Protopterus 3-5-4. 

 Lepidosiren 6-5 - 7. 

 Axolotl 2. 



Salamandra maculosa 4. 

 Triton 1-8. 

 Necturus 6. 



Hypogeophis alternans 4-5. 

 H. rostratus 7-8. 

 Xenopus laevis 1-5. 

 Pipa 6-7. 



Alytes obstetricans 3-5. 

 Pelobates fuscus 1-5. 

 Bufo lentiginosus 1. 

 Hyla goeldii 4. 

 Nototrema fissipes 10. 

 Paludicola fuscomaculata 1. 

 Engystoma ovale 1-25. 

 Cornufer salomonis 5. 

 Rhacophorus reinwardtii 3. 

 Eana temporaria 2. 

 iJ. opisthodon 6 - 10. 



Within the limits of a single genus different species may show 

 marked differences in the size of their eggs, e.#. the Teleostean fish 

 Arius australis has eggs a little over 3 mm. in diameter (Semon) 

 while in the case of A. hoekii they measure over 10 mm. in diameter 

 and in A. commersonii as much as 18 mm. 



Even within the limits of a single species quite measurable, 

 though less conspicuous, differences in size exist between the eggs 

 of different females, and the same holds also, though to a far less 

 extent, for the individual eggs laid by a single female. 



The differences in size which have just been alluded to are 

 correlated with the fact that the egg of the Vertebrate carries in 

 its cytoplasm a less or greater amount of reserve food-material or 

 yolk. The presence of a readily available supply of food within the 

 egg carries with it the immense advantage of freeing the young 



Amphioxus 1. 

 Petromyzon 1. 



Bdellostoma 14 - 29 x 7 - 10-5. 

 Prisliurus melanostomus 16. 

 Acanthias 35 - 40. 

 'Japanese Lamnid ? (Doflein) 220. 

 Torpedo ocellata 20 - 25. 

 Polypterus 1-1. 

 Acipenser 2-2-8. 

 Lepidosteus 3. 

 Amia 2-5-3x2-2-5. 

 Boccus labrax 1-4. 

 Mullus surmuletus -9. 

 Cottus scorpius 1-75. 

 Trigla gurnardus 1-5. 

 Agonus eataphractus 1-8. 

 Trachinus vipera 1-3. 

 Scomber scombrus 1-2. 

 Gobius minutus 1 — 1-4. 

 Cyclopterus lumpus 2-5. 

 Anarrhichas lupus 5-5 - 6. 

 Pholis gunnellus 1-7. 

 Gadus collaris 1-4. 

 G. aeglefinus 1-4. 

 G. virens 1-1. 

 Motella mustela -7. 

 Brosmius brosme 1-3. 

 Ammodytes lanceolatus -76. 

 Hippoglossus vulgaris 3-3-8. 



