In normally fertilized eggs the development of the aster is attributed to a substance carried into the egg by the spermatozoon. The aster first makes its appearance in the form of diminutive radiations surrounding the neck-piece of the spermatozoon within a few minutes after it has entered the egg. The writer 1 has shown that the formation of the radiations is accompanied by a jellying of the c...

Brandstätter, Gigerenzer and Hertwig (2006) put forward the priority heuristic (PH) as a fast and frugal heuristic for decisions under risk. According to the PH, individuals do not make trade-offs between gains and probabilities, as proposed by expected utility models such as cumulative prospect theory (CPT), but use information in a non-compensatory manner and ignore information. We conducted ...

With the advent of molecular phylogenetic techniques the polyphyly of naked filose amoebae has been proven. They are interspersed in several supergroups of eukaryotes and most of them already found their place within the tree of life. Although the 'vampire amoebae' have attracted interest since the middle of the 19th century, the phylogenetic position and even the monophyly of this traditional ...

Follicular oocytes and penetrated eggs of several mammalian species have been the subject of numerous electron microscope studies (rat: Sotelo 1959, Sotelo and Porter 1959, Franchi 1960, Odor and Renninger 1960, Szollosi and Ris 1961, Guinea pig: Anderson and Beams 1960, Adams and Hertwig 1964, Austin 1965. Barron and Franklin 1968. cat: Liss 1964. man: Stegner and Waternberg 1961, Zamboni et a...

We conducted a meta-analysis of 17 studies that tested for an association between grandparental survival and grandchild survival in patrilineal populations. Using two different methodologies, we found that the survival of the maternal grandmother and grandfather, but not the paternal grandmother and grandfather, was associated with decreased grandoffspring mortality. These results are consisten...

Shaping the primordia during development relies on forces and mechanisms able to control cell segregation. In the imaginal discs of Drosophila the cellular populations that will give rise to the dorsal and ventral parts on the wing blade are segregated and do not intermingle. A cellular population that becomes specified by the boundary of the dorsal and ventral cellular domains, the so-called o...