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If pangenesis operated properly and the gemmules were transferred, he predicted that the offspring from those rabbits would not breed true.
This is also a wonderful example of what Karl Popper (1963) called "conjecture and refutation," an intellectual process whereby ideas related to the underlying principle (in this case the gemmules of pangenesis) are proposed and then subjected to experiment in an attempt to reject them.
Gemmules were lightly visible throughout the sample and were brown to black in color (Figure 1, left).
Hatching of freshwater sponge gemmules after low temperature exposure: Ephydatia mulleri (Porifera: Spongillidae).
The Neotropical materials conform all the characteristics proposed for the genus but show consistent larger size of spicules and gemmules besides different shape and size of the sponges when compared to the Ethiopian species.
navicella found in the stomach contents of the fish Hipostomus regania (armored catfish) and Megalancystrus aculetatus (pineapple catfish) also originated from the region at the head of the lake and consisted of pieces of skeleton with gemmules, indicating detachment from firm crusts settled on rocky substrates.
aspinosa was tentative, as gemmules are required for positive confirmation; and we could not find any.
fragilis is well-suited for use in investigating these mechanisms because diapause in its gemmules is easily manipulated and is quite distinct from quiescence (Fell, 1987), a metabolically arrested condition promoted directly by environmental insult.
Finally, we measured ATP, ADP, and AMP in post-diapause gemmules to gain insight into the adenylate status during development.
The most interesting aspect of pangenesis (as shown in Figure 1) is that if some environmental stimulus caused a change in a body part, either by injury or by use and/or disuse, the "new" gemmules produced by that part would be different from those that would originally have developed there.
For instance, by assuming that gemmules could lie dormant for generations, "reversion" (the sudden reappearance of old traits) is easily explained.
The physiological state of the gemmules from Eunapius changes with time and can be divided into three distinct stages: (1) diapause, (2) quiescence, and (3) germination (Fell, 1987).