Investigation of sensory interaction in the hooded rat

An attempt was made to determine the effects of tone on the visual acuity threshold of the rat. Acuity thresholds were ascertained using the Lashley jumping stand with black and white stimulus cards. A pure tone of 7,500 cps at three intensity levels was introduced as accessory stimulus. The results indicated (1) no consistent lowering of S's visual acuity by the introduction of a tone, (2) no within- S differences between tone and no tone when the above threshold and threshold stimuli were analyzed separately, (3) increasingly better performance from low to medium intensities with a decrease in performance at the higher intensity level.

Morphological differences between Chironomus interinctus Skuse and C.paratinctus, sp.nov., with descriptions and a key to the subgenus Kiefferulus (Diptera: Nematocera)

Previous cytological studies of material identified as C. intertinctus (Skuse) had shown that two species were present. Subsequently it has been found that the larvae of the two species may be recognized by the shape of the anal gills and the adults by the anterior leg ratios of femur to tibia and basitarsus to tibia. The females may also be 'recognized by the colouring of the thoracic stripes. C. intertinctus is redescribed and the second species is described as C. paratinctus, sp. nov. The key to the Australian species of the subgenus Kiefferulus is also corrected and the new species included.

The cytology and arval morphology of the Victorian representatives of the subgenus Kiefferulus of the genus Chironmus (Diptera: Nematocera)

The larvae of C. martini, C. intertinctus, and the Botanic Gardens species can be distinguished from other Victorian "blood worms" by the structure of the hypostomial plate and the presence of only one pair of blood gills. It is also the case that the larvae of any one species differ from those of the other two in the average length of the fullgrown larva, the length of the blood gills, and the presence of a feeding brush in C. martini. In the adult form the Botanic Gardens species is taxonomically identical with C. intertinctus. All three species possess the usual four salivary gland chromosomes and each species is quite polymorphic. Twelve inversions are known from C. intertinctus, six from the Botanic Gardens species, and nine from C. martini, which is unusual in being polymorphic for three duplications or deficiencies. It is suggested that the similarity between C. intertinctus and the Botanic Gardens species is due to convergence because of their similar ecology.

Interrelation of Inversion Systems in the Midge Chironomus Intertinctus (Diptera: Nematocera) 1. A Sex-Linked Inversion

One of the inversions in Chironomus (Kiefferulus) intertinctus Skuse, the Corio inversion in chromosone III, is closely linked to the sex-determining region. Different selective values in males and females result in the Standard sequence being more common in the Y -chromosomes while the Corio sequence is more common in the X-chromosomes. In a population from Echuca, Vic., only the Standard sequence occurs in the Y-chromosomes.