EMBRYOLOGY OF THE LOWER VEETEBKATES <n. 



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 

 M'Intosh and Masterman, Bashford Dean, Boulenger, Budgett, 

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

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



APPROXIMATE DIAMETER OF EGG (IN MILLIMETRES) 

 OF VARIOUS FISHES AND AMPHIBIANS 



Amphioxus -I. f 



Petromyzon 1. 



Bdellostoma 14 - 29 x 7 - 10-5. 



Pristiurus melanostomus 16. 



Acanthias 35 - 40. 



Japanese Lamnid ? (Doflein) 220. 



Torpedd ocellata 20 - 25. 



Polypterus 1-1. 



Acipenser 2 2-8. 



Lepidosteux 3. 



Amia 2-5 -3 x 2-2-5. 



Boccus labrax 1-4. 



Mullus surmuletns -9. 



Cottus scorpius l-7.~>. 



Trigla yurnardus 1-5. 



Ayonus cataphractus 1-8. 



Trachinus vipera 1-3. 



Scomber scombrus 1-2. 



Gobius minutus 1 1-4. 



Cyclopterus lumpus 2-5. 



Anarrhicha* //'y /</. 5-.") - 6. 



Pholis yunnellus 1 -7. 



Gadns collaris 1 -4. 



(?. aegli'/iit ".< 1 1. 



6r. virens 1-1. 



Motella mustela -7. 



Brosrnius brosrne 1-3. 



Ammodylea lanceolatus -70. 



3-8. 



Jjothus maximus 1. 

 Pleuronectes platessa 1 s. 

 P. microcephaly^ 1-3. 

 /'. limanda -75. 

 Solea vulgaris 1-2. 

 Clupea liarengus -9-1. 

 (7. sprattus -1. 

 Ceratodus 2-8. 

 Protopterus 3-5-4. 

 Lepidosiren 6-5 - 7. 

 Axolotl 2. 



Salamandra maculosa 4. 

 Trflun 1-8. 

 Necturus 6. 



Hypoyeophis altemans 4-5. 

 //. restrains 7-8. 

 Xenopns laevis 1-5. 

 Pipa 6-7. 



Alytes obstetricans 3 - 5. 

 Pelobates fuscm 1-5. 

 /?it/o lentiyi IHMHX 1. 

 .ff?//a goeldii 4. 

 Nototrenia jisxi i>> -.- 1 < i. 

 Paludicold fuKomaculata \. 

 Enyystoma ovale 1-25. 

 Cornufer aalomonit ">. 

 Rhacophorus n/nir,ir</t// 3. 

 /Aow ft ntiinr<irH< "2. 

 If. fpisthiHlnn 6-10. 



Within the limits of a single genus different species may show 

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

 Arius auxlruli* has eggs a little over 3 mm. in diameter Semon 

 while iii the ease of ,-/. Inti'kil tlioy measure over 10 mm. in diameter 

 and in J. r/,/// /////*..//// as mueh as 18 mm. 



l-A'en within the limits of ;( single sj.ccies tiuite measurable, 

 though less COD SpiOUOUfl/ differences in si/e exist, between the e'_;-'_rs 

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



it. for the individual e^s laid by a single female. 



The dilferenee.^ in H/C \\hieh haYe just been alluded to are 



eoireluliMl with the fact that, the egg "! the X'ertebrate eai'i'ies in 



\!o|ila-m ;i ! DSatei amount of reserve fond material or 



yolk. The pie eOCe Of a readily available supply of to. id uilhin the 



, ilh it I he immense advantage of freeing t I 



