The Arachnomorpha or Arachnata concepts have resolved Trilobita as most closely related to Chelicerata amongst extant Arthropoda. An alternative position of trilobites in the stem lineage of Mandibulata is suggested by their pattern of head tagmosis. The antennae of trilobites and Mandibulata are considered non-homologous with the antennae of Onychophora and stem lineage Euarthropoda: they represent ‘secondary ’ and ‘primary antennae’, respectively. In extant taxa, ‘secondary antennae ’ are deutocerebral, post-ocular, and are connected to deutocerebral olfactory neuropils, whereas ‘primary antennae ’ are pre-ocular and connected to protocerebral olfactory neuropils. In fossils, an insertion at the anterolateral margin of the hypostome rather than more anteriorly on the head allows ‘secondary antennae ’ to be identified. A deutocerebral mouthpart, of which the onychophoran jaw and the chelicera are examples, is regarded as plesiomorphic for Arthropoda. A loss of ‘primary antennae ’ and modification of the deutocerebral mouthpart into a sensory antenna defines the Mandibulata. Trilobites share a ‘secondary antenna ’ and a clearly-delimited head tagma with mandibulates. Given the extensive homoplasy forced by the Arachnata concept (reversals in pycnogonids and arachnids), a trilobite/mandibulate alliance may be better supported. Dedicated to Fred Schram on the occasion of his retirement. Our article challenges canonical views about arthropods, and we were forced to question ideas that we have long considered the best explanation of facts. In doing so, we venture into a territory from which Fred Schram has never shied away. Fred’s synthesis of data from living and fossil arthropods, his efforts to integrate classical morphological and evo-devo perspectives, and his willingness to explore dangerous ideas have inspired our reappraisal of the trilobite problem. 1

SUMMARY We examine terminal addition, the process of addition of serial elements in a posterior subterminal growth zone during animal development, across modern taxa and fossil material. We argue that terminal addition was the basal condition in Bilateria, and that modification of terminal addition was an important component of the rapid Cambrian evolu-tion of novel bilaterian morphology. We categorize the often-convergent modifications of terminal addition from the presumed ancestral condition. Our focus on terminal addition and its modification highlights trends in the history of animal evolution evident in the fossil record. These trends appear to be the product of departure from the initial terminal addition state, as is evident in evolutionary patterns within-fossil groups such as trilobites, but is also more generally related to shifts in types of morphologic change through the early Phanerozoic. Our argument is contingent on dates of metazoan divergence that are roughly convergent with the first appearance of metazoan fossils in the latest Proterozoic and Cambrian, as well as on an inference of homology of terminal addition across bilaterian Metazoa.

Cytological male sterility is a useful trait in plant breeding, especially in medicinal plants such as Cassia angustifolia, Commiphora wightii, Asparagus racemosus.Abnormalities appeared to be the cause of male sterility in plants, we carried out this research in an attempt to make clear the characteristics and inheritance of this male sterility. In Plantago ovata germplasm cytoplasmic abnormality was found to be the cause of abnormality. cytomixis varied from 2 % to 48 % in plants. Maximum numbers of PMCs carrying B-chromosomes were recorded in male sterile plants of line JI-214(62%). No B-chromosomes were observed in fertile, sterile and partial male sterile line of JI-107 and maximum abnormal chromosomal segregation was recorded in JI-206. These cytological abnormality parameters can be used for hetrosis breeding and hybrid seed production to improve quality of psyllium. Key words: P. ovate, cytoplasmic male sterility, pollen mother cell, sex

Morphological requirements in limulid and decapod gills: A case study in deducing the function of lamellipedian exopod lamellae

of the caudal exoskeleton of the pliomerid trilobite Hintzeia