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When the Great Depression struck in 1929, many people believed that the cause was the rapid development of new technologies such as the assembly line, which eliminated people's jobs while [...]

The Red Grouper Epinephelus moriois an ecologically and economically important Gulf of Mexico reef fish species. The well‐documented excavation behavior of this species generates several‐meter‐wide holes that serve as habitat in otherwise structureless areas. These mesohabitats are notably dense within the Steamboat Lumps (SL) Marine Protected Area (MPA) in the eastern Gulf of Mexico. Previous work in the SL‐MPAused high‐resolution multibeam bathymetry to analyze changes in hole density and structure (width, height, and slope) between 2006 and 2009. The present study utilizes additional multibeam data collected in 2017 to further these analyses. Overall, the density of holes within the SL‐MPAcontinued to increase, but no definite trend in structural changes could be identified. Additionally, a towed camera was used to directly observe 95 holes, of which 63 had detectable reef fishes. Within the occupied holes, approximately 46% had a Red Grouper or other grouper species (Epinephelidae) present. The most frequently observed species within the occupied holes were invasive lionfish Pteroisspp., which were present in 84% of the holes. The increasing density of Red Grouper holes in the SL‐MPAindicates that the closure of the area may be resulting in a more robust local population of this species. However, quick colonization of the holes by lionfish has occurred, and additional studies are necessary to determine the impact of this on grouper and other native reef fish populations found within this type of uniquely created habitat.

During mitosis, chromosome segregation is regulated by a spindle checkpoint mechanism. This checkpoint delays anaphase until all kinetochores are captured by microtubules from both spindle poles, chromosomes congress to the metaphase plate, and the tension between kinetochores and their attached microtubules is properly sensed. Although the spindle checkpoint can be activated in many different cell types, the role of this regulatory mechanism in rapidly dividing embryonic animal cells has remained controversial. Here, using time-lapse imaging of live embryonic cells, we show that chemical or mutational disruption of the mitotic spindle in early Caenorhabditis elegans embryos delays progression through mitosis. By reducing the function of conserved checkpoint genes in mutant embryos with defective mitotic spindles, we show that these delays require the spindle checkpoint. In the absence of a functional checkpoint, more severe defects in chromosome segregation are observed in mutants with abnormal mitotic spindles. We also show that the conserved kinesin CeMCAK, the CENP-F-related proteins HCP-1 and HCP-2, and the core kinetochore protein CeCENP-C all are required for this checkpoint. Our analysis indicates that spindle checkpoint mechanisms are functional in the rapidly dividing cells of an early animal embryo and that this checkpoint can prevent chromosome segregation defects during mitosis.

THE expedition sent by the German Governwent to observe the Transit of Venus at Kerguelen's Land has brought home a noble series of specimens.

THERE is a slight error in your account of the disposition of Prof. Willis with regard to his mechanical models in your last impression (p. 14).