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ÖELLACHER * from his studies on salmon trout agreed with LEREBOULLET. 
Barcray 3° described a newly born shark that was double from its head end 
to the navel. Rauper ** examined one double chick and four trout embryos. 
In the latter the following conditions prevailed: 
1. Head partially divided. 
2. Head divided to pectoral fin and separated at an angle of about 45°. 
3. Embryo cleft almost to its tail with the parts at an angle of about 
75°. The embryos were of unequal size. 
4. Cleft to the tail and embryos of unequal size. 
RatHKe *7 found only one double monster in his study of fishes. The 
embryos were regular in formation, but of unequal size. The larger alone 
had a yolk-sack. The smaller was connected by a delicate strand from its 
umbilical vesicle to the yolk sac of the larger. SPRENGEL ** described a double 
salamander attached to each other at heads and tails, while Braun 3° observed 
in certain reptiles two young doubles belonging to the same parent. Each 
of the first pair was about 15mm. long in its own amnion and at an angle 
of about 130° to the other. The embryos of the other pair were parallel in 
the same amnion. 
Among the most recent monstrosities are the following: 
Reese ® found a crocodile’s egg that was apparently normal. Upon 
examination two embryos were seen upon the same yolk. These were almost 
at a right angle to each other and each embryo possessed a vascular area. 
JoseEpa *: found a double egg of Scyllium. This egg contained two yolks of 
average size in early, stages of development. Batik * describes a double spinal 
cord in a marsupial embryo of 5 mm. length. 
KAESTNER ** carried on some interesting experiments with hen’s eggs to 
determine the effect cold and interruptions of incubation with reference to 
the formation of malformations. Normal development takes place between 
35° and 39° C. Below 35°C. malformations occur. Parma in 1869 found that 
interruptions of incubation by cooling predisposed to the development of mal- 
formations. KAESTNER found that eggs would develop between 28° and 43° C.; 
below 28° development is arrested, but the embryos do not die, while above 
43° C. the embryos die. From his experiments he found that eggs could be 
taken from the incubator at various stages, cooled to 5° or 10° C. and when 
replaced in the incubator development would continue. 
There are four respiratory stages as determined by Sopaim BAxonrnc.** 
1. Breathing directly through tissue (Infusoria). 
2. Breathing by the circulation of hemoglobinless blood (white blooded 
animals). 
3. Breathing by means of a yolk sac circulation (cold blooded animals). 
4. Breathing by means of an allantoic circulation (warm blooded animals). 
Karstner #5 found that during the first breathing stage, chick embryos 
could lie for long periods at low temperature and when returned to the 
incubator would continue to develop; when the embryo has reached the 
allantoic breathing stage, however, the effects are usually disastrous as the 
embryo cannot stand great loss or want of oxygen or heat at this stage. © 
He found that cooling at 10° C. seemed to be more injurious than lowering — 

